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B   4   521 

GONADECTOMY 


IN  RELATION  TO  THE 


SECONDARY  SEXUAL  CHARACTERS  OF  SOME 
DOMESTIC  BIRDS 


BY  H.  D.)  GOODAJJE 

Of  the  Massachusetts  Agricultural  Experiment  Station 


PUBLISHED  BY  THE  CAENEGIE  INSTITUTION  OF  WASHINGTON 
WASHINGTON,  1916 


GONADECTOMY 

IN  RELATION  TO  THE 

SECONDARY  SEXUAL  CHARACTERS  OF  SOME 
DOMESTIC  BIRDS 


BY  H.  D.LGOQDALE 

Of  the  Massachusetts  Agricultural  Experiment  Station 


PUBLISHED  BY  THE  CARNEGIE  INSTITUTION  OF  WASHINGTON 
WASHINGTON,  1916 


CARNEGIE  INSTITUTION  OF  WASHINGTON 
PUBLICATION  No.  243. 


PAPER  No.  27  OF  THE  STATION  FOB  EXPERIMENTAL  EVOLUTION  AT 
COLD  SPRING  HARBOR,  NEW  YORK 


PRESS  OF  GIBSON  BROTHERS  INC. 
WASHINGTON 


CONTENTS. 


PAGE. 

Introduction 5 

The   material 7 

Juvenile  characters 9 

The  operation 10 

The  anesthetic 10 

Preliminary  steps 11 

Removal  of  testes 11 

Removal  of  ovary 12 

Description  of  cases 13 

Ducks 13 

Female  ducks  completely  ovariotomized 14 

Female  ducks  partially  ovariotomized 17 

Male  ducks  completely  orchidotomized 18 

Male  ducks  partially  orchidotomized 20 

Domestic  fowl 21 

Female  fowl  completely  ovariotomized 21 

Female  fowl  partially  ovariotomized 25 

Male  fowl  partially  or  completely  orchidotomized 26 

Age  in  relation  to  gonadectomy 31 

The  age  of  the  feather  germ  in  relation  to  the  type  of  feather  developed 31 

Two  types  of  females  resulting  from  ovariotomy 34 

Effects  of  gonadectomy  on  particular  parts  of  the  body 36 

Effect  on  plumage 36 

Effect  on  head  furnishings 36 

Effect  on  spurs 38 

Effects  on  the  voice  and  associated  organs 39 

Effect  on  the  molt 39 

Effect  on  color  of  the  mandible 41 

Effect  on  size 41 

Effect  on  behavior 42 

Effect  on  accessory  organs  of  reproduction 42 

Effect  on  the  bursa  Fabricii 43 

Occurrence  of  characters  of  one  sex  in  individuals  of  the  opposite  sex  that  are  other- 
wise normal 43 

Male  characters  in  the  otherwise  normal  female 43 

Female  characters  in  the  otherwise  normal  male 45 

Hen-feathered  males 45 

Inheritance  of  secondary  sexual  characters 46 

Is  the  female  bird  a  suppressed  hermaphrodite? 47 

The  relation  between  breeding  and  gonadectomy 48 

Darwin's  and  Wallace's  theories  of  the  origin  of  secondary  sexual  characters 49 

Nature  and  mode  of  the  ovarian  secretion 49 

Relation  between  the  gonads  and  the  secondary  sexual  characters  in  other  groups ....  51 

Summary 51 

Literature  cited 52 

3 


r:  r«.i«jn 

D  i .  «J-i  •*  «> 


GONADECTOMY  IN  RELATION  TO  THE  SECONDARY  SEXUAL 
CHARACTERS  OF  SOME  DOMESTIC  BIRDS.1 


INTRODUCTION. 

It  has  been  long  known  that  an  intimate  relation  exists  between  the 
primary  sexual  organs  of  certain  animals  and  their  secondary  sexual 
characters.  Until  recent  years,  however,  there  has  been  considerable 
doubt  as  to  the  interpretation  of  many  of  the  effects  of  castration — 
i.  e.,  as  to  whether  the  effect  tended  toward  the  appearance  of  char- 
acters belonging  to  the  opposite  sex.  In  particular,  there  has  been  a 
dispute  as  to  whether  certain  characters,  such  as  the  small  comb  of  the 
capon,  were  to  be  considered  juvenile  or  female.  In  birds  the  occur- 
rence of  individuals  with  the  plumage  and  other  characters  of  the  male, 
but  having  the  sexual  organs  of  the  female,  have  attracted  a  great  deal 
of  attention.  Recently,  Guthrie  (1910)  has  described  a  hen  with  male 
plumage  following  ovariotomy,  while  Fitzsimons  (1912)  has  reported 
like  results  in  the  ostrich. 

Very  often,  and  perhaps  always,  the  records  state  that  the  ovaries  of 
male-plumaged  females  occurring  in  nature  have  degenerated  to  a 
greater  or  less  degree,  and  from  this  it  has  been  inferred  that  the  occur- 
rence of  the  male  plumage  was  in  some  way  or  other  associated  with  the 
degeneration  of  the  ovary.  On  the  other  hand,  the  sporadic  occur- 
rence of  birds  with  the  external  characters  of  the  female  and  the  internal 
sexual  organs  of  the  male  is  relatively  uncommon  in  races  such  as 
pheasants  or  domestic  fowl.  As  a  rule  such  males,  whose  primary 
sexual  organs  are  perfectly  normal,  exhibit  only  one  or  two  female 
characters,  the  remainder  of  their  secondary  sexual  characters  being 
those  of  the  normal  male.  Female  characters  may  also  be  normal  to 
the  juvenile  male.  Moreover,  it  has  been  shown  in  the  case  of  hen- 
feathered  males  of  the  domestic  fowl  that  this  character  is  inherited  in 
a  definite  fashion.  The  occurrence  of  male  birds  with  the  secondary 
sexual  characters  of  the  female,  where  these  characters  are  distinct 
from  those  of  the  juvenile  male,  are  extremely  rare.  It  seems  highly 
probable  that,  except  in  the  very  rarest  of  instances,  female-feathered 
males  are  in  an  entirely  different  category  from  male-feathered  females. 
(However,  cf.  Morgan,  1915.)  Nevertheless,  races  exist,  such  as  the 
bobolink,  in  which  the  males  may  become  nearly  or  quite  indistin- 
guishable from  the  females  at  certain  seasons  of  the  year. 

1This  paper  is  based  on  work  done  at  the  Station  for  Experimental  Evolution  of  the  Carnegie 
Institution  of  Washington,  while  the  author  was  a  member  of  the  staff  at  that  station.  It  has 
been  necessary,  however,  to  include  some  observations  made  at  the  Massachusetts  Agricultural 
Experiment  Station,  which  relate  either  to  matters  of  detail  or  confirm  results  previously  obtained. 

5 


s6?  ,«*  ^.*4SJONADEerOMY   IN   RELATION   TO   THE    SECONDARY 

Special  attention  is  directed  to  those  statements  in  the  literature 
according  to  which  the  secondary  sexual  characters  of  the  male  bird 
do  not  develop  after  castration.  Thus,  Marshall  writes: 

"It  is  well  known  that  caponization  or  the  removal  of  the  testes  in  fowl 
arrests  the  development  of  the  comb  and  spurs  and  other  secondary  male 
characters  which  are  normally  present  in  the  cock."1 

As  far  as  I  can  learn,  the  only  characters  for  which  the  statement 
holds  true  are  the  comb  and  wattles,  the  crowing  instinct,  and  the 
sexual  reactions,  and  even  here  it  appears  that  the  last  two  are  merely 
suppressed  but  not  really  absent,  since  both  are  occasionally  observed 
in  perfect  capons.  Certainly,  whatever  foundation  there  may  be  for 
such  statements  regarding  the  spurs  and  plumage  is  to  be  found  in 
some  other  circumstances  than  castration.  A  further  discussion  of  the 
point  is  given  below. 

It  has  not  been  easily  possible  to  verify  by  experiment  the  inferences 
regarding  the  condition  of  the  ovary  in  relation  to  the  plumage  and 
other  secondary  sexual  characters,  because  its  complete  experimental 
destruction  or  removal  has  involved  some  practical  difficulties,  owing 
to  its  situation  upon  some  of  the  main  blood-vessels  of  the  abdominal 
cavity.  On  the  other  hand,  the  experimental  removal  of  the  testes 
is  accomplished  with  such  ease  that  it  has  long  been  a  common  practice 
among  poultry  growers  to  castrate  their  surplus  cockerels  because  of 
improved  eating  qualities.  This  result,  however,  may  be  secured  with- 
out an  absolutely  complete  removal  of  the  testes  and  epididymis;  that 
is,  good  capons  are  sometimes  found  with  a  small  amount  of  tissue  on 
the  site  of  the  testes. 

The  effects  of  castration  on  the  secondary  sexual  characters  of  the 
cock  have  been  studied  by  a  number  of  observers,  who  report,  in  general, 
that,  with  the  exception  of  head  furnishings,  the  characters  of  the  male 
develop  in  nearly  the  same  way  as  those  of  the  normal  male.  It  is  true 
that  in  some  instances  it  has  been  recorded  that  these  characters,  such 
as  spurs,  luster,  long  feathers,  etc.,  either  fail  to  develop  or  develop 
imperfectly.  However,  anyone  with  a  moderately  wide  acquaintance 
with  poultry  can  easily  observe  many  instances  of  the  same  sort  among 
males  that  have  not  been  castrated :  Plumage  which  lacks  in  luster  is 
common  among  males  of  low  vitality,  though  otherwise  normal;  spurs 
develop  very  slowly  in  some  races ;  the  males  of  some  breeds  have  relatively 
short  sickle  feathers,  and  so  on.  In  other  words,  the  characteristics 
described  presumably  have  nothing  to  do  with  the  results  of  castration. 

True  hermaphrodites  may  also  exhibit  characters  of  both  sexes,  but 
since  they  have  the  primary  organs  of  both  sexes  present  they  can  not 
well  afford  critical  evidence  on  the  points  involved  in  this  paper.  The 
possibility  that  these  may  be  genetically  females  will  be  discussed  in 
the  body  of  this  paper. 

italics  mine. 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  7 

The  terms  primary,  accessory,  and  secondary  sexual  characters  have 
been  used  in  their  usual  significance — i.  e.,  the  primary  organs  are  the 
testes  in  the  male,  the  ovary  in  the  female.  The  accessory  characters 
are  the  vasa  deferentia  and  the  penis  or  papillae  in  the  male,  the  oviduct 
in  the  female.  The  secondary  sexual  characters  include  in  a  broad 
sense  all  the  other  characters  in  which  the  sexes  differ.  No  attempt, 
however,  has  been  made  to  cover  so  wide  a  field,  but  attention  has  been 
limited  to  the  more  obvious  characters.  There  are  many  details  of 
interest  that  thus  far  it  has  been  impossible  to  study  thoroughly  and 
which  will  have  to  be  left  for  the  future. 

In  describing  results,  the  words  "male"  and  " female"  have  often 
been  used  in  a  purely  descriptive  sense.  Thus,  "male"  feathers  in  a 
female  means  of  course  that  such  feathers  are  indistinguishable  from 
similar  feathers  found  in  males,  and  so  on.  No  implication  is  made 
as  to  the  actual  nature  of  the  feathers. 

THE  MATERIAL. 

During  the  course  of  the  work,  experiments  have  been  performed  on 
both  pure-bred  and  cross-bred  birds  of  both  sexes,  a  majority  of  which 
have  been  pedigreed.  The  cross-bred  ducks  were  derived  originally  from 
Rouen  and  Pekin  crossed  reciprocally.  The  cross-bred  fowl  were  mostly 
from  a  White  Plymouth  Rock  and  Brown  Leghorn  cross.  The  results 
obtained  from  the  cross-breds  have  agreed  in  a  general  way  with  those 
obtained  from  pure-bred  birds.  In  detail,  however,  their  use  intro- 
duced some  complications  which  are  discussed  in  the  body  of  the  paper. 
For  the  pure  breeds,  Rouen  ducks  and  Brown  Leghorns  were  selected, 
not  only  because  they  represent  the  acme  of  sexual  dimorphism  among 
easily  available  domestic  birds,  but  because  they  offered  an  opportunity 
to  determine  whether  or  not  the  male  assumes  female  characteristics  as 
a  result  of  castration  or  whether  the  so-called  female  characters  are  in 
reality  juvenile.  Moreover,  it  seemed  wise  in  the  case  of  the  fowl  to  have 
birds  that  were  relatively  homogeneous  in  respect  to  the  size  and  form  of 
comb,  particularly  for  the  work  with  the  male.  Previous  observers  of 
the  effects  of  caponization,  so  far  as  I  have  had  access  to  their  papers, 
have  not  usually  paid  sufficient  attention  to  the  variety  of  fowl  used. 
As  it  happens,  the  variety  of  birds  used  for  capons,  at  least  in  this 
country,  are  mainly  the  small-combed  breeds.  Hence,  at  best,  the 
capons  would  have  relatively  small  combs.  The  Leghorns,  however, 
have  large  combs  in  each  sex,  a  feature  which  might  affect  the  size  of 
the  capon's  comb.  Moreover,  in  heredity,  the  small  comb  is  at  least 
partially  dominant  over  the  large — i.  e.,  the  offspring  of  a  cross  between 
a  small-combed  and  a  large-combed  race  approximated  in  size  that  of 
the  small-combed  parent.1 

Unpublished  data. 


8  GONADECTOMY   IN   RELATION   TO   THE   SECONDARY 

The  plumage  of  the  birds  used  in  these  experiments  requires  especial 
attention,  partly  because  of  the  marked  difference  in  the  sexes,  partly 
because  of  its  complex  nature  and  the  succession  of  plumages  during 
the  life  of  each  individual.  At  least  two  sets  of  patterns  influence  the 
general  color  of  the  bird.  There  is,  first,  the  body  pattern,  which 
depends  upon  the  arrangement  of  feathers  of  different  form  and  color 
upon  the  body;  superimposed  on  this  body  pattern  are  the  patterns  of 
the  individual  feathers.  Any  one  follicle,  however,  may  produce  dif- 
ferent kinds  of  feathers  at  different  periods  in  the  life  of  the  bird.  Thus 
all  normal  individuals,  both  ducks  and  fowl,  experience  a  succession  of 
plumage  from  the  time  they  emerge  from  the  egg  to  old  age.  What 
constitutes  the  adult  plumage  is  a  little  difficult  to  say,  for  in  some 
cases  no  plumage  is  quite  like  that  which  preceded  it.  In  some  varie- 
ties the  difference  between  the  plumage  of  the  first  and  second  winters 
is  greater  than  that  between  the  second  and  third.  However,  in  both 
ducks  and  fowls  the  strictly  juvenile  plumages  are  quite  distinct  from 
the  first  mature  plumage,  so  that  for  present  purposes  the  plumage 
worn  during  the  first  winter  by  spring-hatched  birds  may  be  considered 
adult.  In  ducks  there  are  three  plumages :  down,  juvenile,  and  adult. 
In  Brown  Leghorns  there  are  four:  down,  chick,  juvenile,  and  adult. 
The  distinctions  between  these  plumages,  as  will  be  observed  from  the 
appended  descriptions,  are  for  the  most  part  sharp  and  clean-cut  at 
the  height  of  development.  Usually,  however,  because  the  plumage  is 
changed  piecemeal,  two  succeeding  stages  are  intermingled.  The 
descriptions  are  not  intended  to  cover  all  details  or  all  variations. 

ROUEN  DUCKS. 

Down  plumage. — Sexes  indistinguishable;  feathers  in  the  form  of  down.  Body :  dull  black 
dorsally;  ventrally,  yellow  with  a  dark  stripe  through  the  eye  and  a  similar  one  a  little  lower 
on  the  cheek  and  four  dull  yellow  spots  on  the  dorsal  side  of  the  body  (plate  vn,  fig.  D) . 

Juvenile1  plumage. — Sexes  similar  but  distinguishable;  the  down  gives  way  to  ordinary 
feathers;  head  stripes  persist  but  the  spots  disappear;  contour  feathers  dull  black,  with 
brown  margins  in  the  female.  The  male  is  similar,  except  that  there  are  no  brown  margins 
on  the  feathers  of  the  rump  and  dorsal  surface  of  the  wing;  the  rump  feathers  are  greenish 
black;  a  few  vermiculated  feathers  are  present  in  various  parts  of  the  body. 

Adult  plumage. — Sexes  quite  unlike.  Female  (plate  n)  :2  head  stripes  persistent ;  entire 
plumage  dull  black  and  brown,  the  feathers  sometimes  penciled  (plate  vi,  o),  sometimes 
marked  irregularly  (plate  vi,  m,) ;  no  well-defined  color  areas.  Male  (plate  i) :  no  head 
stripes;  several  well-defined  color  areas,  viz,  green  head,  brownish  purple  breast,  silver  gray 
ventral  regions,  greenish  black  rump;  remainder  of  dorsal  surface  dull  black.3 

BROWN  LEGHORN  FOWL. 

Down  plumage. — Sexes  indistinguishable;  mid-dorsal  region  rich  reddish-brown  edged 
with  dark  brown  or  black,  becoming  yellowish  ventrally;  a  dark-brown  stripe  passing  through 
the  eye  is  separated  from  the  top  of  the  head  by  a  buff  stripe.  Back  with  a  longitudinal 
stripe  on  each  side  of  buff  and  brown.  Sometimes  the  buff  stripe  is  nearly  white,  sometimes 
the  brown  is  nearly  black. 

xThe  word  "juvenile"  is  used  here  for  all  plumage  phases  of  the  young  and  not  in  the  limited 
sense  used  in  the  preceding  section. 

2In  all  the  figures,  due  allowances  must  be  made  for  the  difficulties  of  reproducing  the  exact 
color  values  of  the  original  specimen. 

'The  speculum,  i.  e.,  iridescent  blue  bar  of  the  wing,  is  alike  in  each  sex. 


SEXUAL    CHARACTERS   OF   SOME    DOMESTIC   BIRDS. 

Chick  plumage. — Sexes  indistinguishable  by  color  alone.  Plumage  as  before,  except  that 
the  remiges  and  rectrices  develop  precociously,  together  with  a  few  feathers  along  the  sides 
of  the  breast  and  belly.  A  few  other  spots  also  develop  feathers  precociously.  The  breast 
feathers  are  buff  or  brown;  the  rectrices  and  remiges  buff  and  brown  mingled  irregularly. 
This  plumage  is  perhaps  a  phase  of  the  down  plumage  due  to  the  precocious  development  of 
the  main  wing  and  tail  feathers. 

Juvenile  plumage. — Sexes  readily  distinguishable.  Female:  buff  breast,  dull- black  pri- 
maries, brown  and  black  secondaries  and  tail  feathers.  Hackle  laced  with  yellow,  the  center 
black  and  yellow  mixed;  remainder  of  the  plumage  brownish  and  dull  black,  closely  inter- 
mingled as  stippling.  Male :  Dorsal  feathers  short,  but  may  be  pointed  at  end  in  late  stages ; 
breast  red  and  black  or  buff  and  black;  rectrices  black,  primaries  black,  secondaries  red  and 
black;  remainder  of  plumage  red  and  black  with  some  indications  of  the  adult  body-pattern. 

Adult. — Sexes  very  different.  The  female  similar  in  color  to  the  female  in  juvenile  plu- 
mage, except  that  as  a  rule  the  stippling  is  much  finer  (plate  vi,  k).  The  male  has  several 
well-marked  body  areas,  viz,  glossy  black  breast  and  belly,  black  wing  front  and  bar  (first 
and  second  row  of  secondary  coverts).  Feathers  of  the  rest  of  wing  and  middle  of  back  red 
with  black  centers,  short  but  pointed.  Saddle  feathers  long  and  pointed  (plate  vi,  I),  with 
black  centers  (sometimes  absent  in  lateral  feathers),  and  red  or  orange  margins;  tail  coverts 
glossy  black,  long  and  curved,  rectrices  black.  Hackles  long  and  pointed,  similar  in  color  to 
saddle  feathers.  The  red  feathers  of  the  back  and  wing  and  the  saddle  hangers  are  char- 
acterized by  having  a  part  of  each  barb  modified  into  a  bristle. 

JUVENILE  CHARACTERS. 

The  characters  of  the  young  are  often  spoken  of  as  identical  with  those 
of  the  female.  In  many  instances  this  is  true,  particularly  for  those 
characters  of  the  adult  male  which  are  absent  in  the  adult  female,  yet 
other  characters  appear  only  in  the  young,  while  a  third  set  appears 
only  in  the  young  male;  the  last  are  sometimes  specific,  sometimes  like 
those  of  the  adult  male.  In  the  Leghorns  there  is  no  stage  in  which  the 
young  male,  as  a  whole,  is  like  an  adult  female,  though  he  may  be 
more  like  his  mother  than  like  his  father  in  that  both  are  brown.  In 
the  down,  also,  he  is  brownish  (as  well  as  his  sister),  but  in  an  entirely 
different  way  from  the  adult  female.  The  young  drake  in  juvenile 
plumage  on  the  whole  resembles  his  mother  far  more  than  his  father, 
just  as  the  latter  in  the  state  of  eclipse  comes  to  resemble  his  mate.  In 
the  down  his  plumage,  like  the  Leghorn's,  is  identical  with  that  of  his 
sister  and  neither  are  at  all  like  their  mother  or  father.  On  the  whole 
very  few  juvenile  characters  in  the  young  male  are  identical  with  those 
of  the  female.  Even  the  young  female  has  many  characters  peculiar 
to  her  age.  In  the  young  male  Brown  Leghorn  the  only  character  almost 
identical  with  a  female  character  is  the  brown  stippling  on  the  feathers 
of  the  dorsal  region  in  many  individuals.  His  breast  feathers  are 
always  red  and  black,  never  entirely  buff.  His  comb  grows  faster 
than  his  sister's  and  is  noticeably  larger  at  a  very  early  age,  three  weeks 
or  less  in  robust  individuals.  The  young  drake  has  head  stripes  like 
his  mother's,  but  this  is  about  the  only  point  on  which  there  can  be  no 
question  of  the  resemblance.  His  ventral  feathers,  while  dull  black 
with  brown  edging  like  his  sister's,  are  not  penciled  like  those  of  the  adult 
female.  On  the  other  hand,  his  mandible  begins  to  change  color  at  a 
very  early  age.  A  few  vermiculated  feathers  occur  on  parts  of  the  body, 


10  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

while  the  feathers  of  his  rump  have  no  brown  edging,  as  in  both  old 
and  young  females. 

The  exact  nature  of  the  juvenile  characters  must  be  taken  into  con- 
sideration when  discussing  the  results  of  castration.  The  mere  fact 
that  a  closer  resemblance  exists  between  the  female  and  the  young  than 
between  the  male  and  the  young  can  not  be  taken  as  an  indication  that 
the  young  are  more  female  than  male.  The  most  obvious  explanation 
of  the  resemblance  is  that  the  characters  of  both  are  protective  and 
that  natural  selection  has  preserved  them. 

THE10PERATION. 

The  operation  in  each  sex  is  very  simple,  the  only  difficulty  being  in 
the  proximity  of  the  great  blood-vessels — the  iliacs  and  the  inferior  vena 
cava — directly  upon  whose  surfaces  lie  the  organs  of  reproduction.  In 
both  males  and  females  the  preliminary  steps  are  identical,  except  that 
for  best  results  the  male  should  be  opened  on  each  side.  The  female  is 
opened  on  the  left  side  only. 

THE  ANESTHETIC. 

The  anesthetic  and  method  of  administering  it  vary  with  the  age 
and  depend  also  upon  whether  the  bird  is  a  duck  or  chicken.  Ether  is 
the  main  dependence  for  most  operations.  This  is  given  by  inserting 
the  head  of  the  bird,  or  sometimes  the  beak  only,  into  a  bottle  contain- 
ing the  anesthetic  on  cotton.  Ducks  have  a  trick  of  holding  their 
breath  the  moment  their  head  is  inserted.  They  will  inhale,  however, 
the  moment  the  bottle  is  withdrawn,  so  that  by  making  false  move- 
ments they  may  be  induced  to  inhale  the  anesthetic.  Aid  may  also 
be  had  by  massaging  the  abdomen  and  chest.  After  a  few  inhalations 
have  taken  place  the  duck  loses  the  power  of  inhibiting  the  respiration 
and  begins  to  breathe  regularly.  With  older  ducks  it  is  sometimes 
difficult  to  give  enough  ether  readily  in  this  way.  Chloroform  conse- 
quently is  used  for  the  first  four  or  five  breaths,  just  enough  to  over- 
come the  duck's  control  of  the  inhibitory  mechanism  of  respiration. 
More  can  not  be  used,  for  chloroform  with  both  ducks  and  fowls  is 
often  quickly  fatal.  Very  young  birds  are  so  susceptible  to  the  influ- 
ence of  ether  that  it  is  difficult  to  keep  them  in  exactly  the  right  con- 
dition. By  skillful  manipulation,  however,  the  bird  may  be  kept  in 
good  working  shape.  With  older  birds  the  period  during  which  the 
ether  is  given  lengthens,  while  the  intervals  during  which  the  ether  is 
kept  away  become  continually  shorter  until,  with  ducks  3  or  4  months 
old,  it  is  necessary  to  give  all  the  ether  they  will  take  after  the  abdom- 
inal cavity  is  opened ;  for  as  soon  as  this  is  done  much  less  ether  appears 
to  be  absorbed  on  account  of  the  structure  of  the  respiratory  mech- 
anism. It  is  usually  advisable  to  have  the  bird  thoroughly  under  an 
anesthetic  before  the  opening  is  made,  otherwise  it  is  often  impossible 
completely  to  narcotize  the  animal. 


SEXUAL    CHARACTERS   OF   SOME    DOMESTIC   BIRDS.  11 

In  determining  the  degree  of  anesthesia,  reliance  is  placed  upon  the 
amount  of  relaxation  of  the  neck,  the  condition  of  the  eyes — i.  e., 
whether  open  or  closed — and  the  rate  and  depth  of  respiration.  With 
good  working  anesthesia  the  neck  is  limp,  the  eyes  closed,  and  the 
respiration  deep  and  regular.  Too  much  ether  is  shown  by  shallow, 
rapid,  but  often  slightly  irregular  respiration.  Too  little  is  indicated 
by  a  rigid  neck  and  often  open  eyes,  though  the  bird  gives  few  other 
indications  of  sensibility.  Rapid  respiration  is  often  observed  with 
too  little  ether. 

PRELIMINARY  STEPS. 

The  bird  is  fastened  to  the  operating  table  by  a  cord  around  both 
wings,  which  are  drawn  over  the  back,  while  the  legs  are  similarly  fas- 
tened, but  stretched  at  a  medium  tension  in  line  with  the  long  axis  of 
the  body.  The  feathers  are  plucked  from  an  area  extending  from  the 
fourth  rib  posteriorly  over  the  thigh  and  from  mid-line  of  the  back  to 
the  center  of  the  breast.  An  oblique  incision  is  made  through  the  skin 
from  near  the  mid-dorsal  line,  slightly  obliquely  downward,  following 
the  anterior  margin  of  the  sartorius;  then  an  incision  is  made  between 
the  last  two  ribs.  This  incision  should  be  as  large  as  necessary  for  con- 
venience and  will  vary  in  different  cases,  care  being  taken  to  avoid 
extending  the  cut  so  far  dorsally  as  to  sever  the  spinal  artery.  The 
ribs  are  drawn  apart  by  hooks  and  chain  or  suitable  spreader. 

REMOVAL  OF  TESTES. 

In  the  male,  except  in  very  young  individuals,  the  area  of  attachment 
of  the  testis  is  small,  proportionally  to  the  size  of  the  organ.  At  the 
age  at  which  the  testes  are  commonly  removed  in  commercial  caponiza- 
tion  the  testes  are  ovoid  in  shape,  while  the  vascular  system  is  slightly 
developed.  The  connective  tissue  is  also  delicate,  so  that  with  modern 
instruments  the  removal  of  the  gonads  is  a  simple  matter.  In  the  adult 
the  vascular  supply  has  become  well  developed,  the  area  of  attach- 
ment absolutely  larger,  while  the  connective  tissues  are  tough,  necessi- 
tating the  use  of  ligatures  and  knives  in  then-  removal.  In  the  very 
young  bird  the  testes  are  delicate;  each  has  the  form  of  a  narrow  cylin- 
der, pointed  at  both  ends,  which  is  attached  along  one  side  to  the  iliac, 
rendering  the  removal  correspondingly  difficult.  It  may  be  readily 
accomplished,  however,  with  a  slender  pair  of  curved  forceps,  but 
much  care  must  be  taken  to  avoid  rupturing  the  iliac  or  the  testicle. 
If  the  latter  happens,  it  becomes  very  difficult  to  make  a  complete 
removal.  The  best  procedure  yet  found  in  removing  these  very  young 
testicles  is  to  get  one  end  started  by  picking  carefully  at  the  union  with 
the  iliac;  the  testicle  can  then  be  peeled  off  by  keeping  hold  of  the 
capsule  on  the  iliac  side  with  the  forceps.  Sometimes  it  may  be  found 
desirable,  after  the  end  has  been  started,  to  push  off  the  testis  with  a  wad 
of  cotton.  With  older  birds  ordinary  caponizing  tools  may  be  used. 


12  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

REMOVAL  OF  OVARY. 

In  the  young  female  the  ovary  is  a  flat  sheet  of  tissue,  attached 
intimately  by  one  surface  to  the  ventral  surface  of  the  left  iliac  and  vena 
cava.  It  may  be  removed  in  the  following  manner:  Tear  open  the 
lateral  peritoneum  with  tenaculum  and  forceps  and  also  the  dorsal 
peritoneum,  which  covers  the  ovary.  Care  should  be  taken  to  see  that 
all  loose  ends  are  removed.  The  dorsal  mesentery  is  then  freed  from 
its  attachment  near  the  iliac,  extending  from  the  anterior  mesenteric 
artery  posteriorly  to  a  point  somewhat  posterior  to  the  end  of  the  ovary. 
This  should  leave  the  ovary  and  environs  free  from  all  membranes  and 
the  ovary  ready  for  removal.  With  a  pair  of  fine-pointed  but  blunt 
forceps  the  rear  end  is  seized  and  gently  pulled  up.  Sometimes  there 
is  a  slight  projection  of  the  ovary  rearward,  which  is  free  from  the  iliac. 
This  greatly  facilitates  the  starting  of  the  ovary.  If  this  projection  is 
wanting  it  will  be  necessary  to  pick  patiently  at  the  end  of  the  ovary 
and  attempt  to  grasp  it  at  its  union  with  the  iliac.  Once  the  end  is 
started,  it  is  possible  to  proceed  more  rapidly.  As  soon  as  a  sufficient 
amount  is  freed  to  furnish  a  secure  grip,  the  end  is  taken  firmly  and  a 
gentle  pull  anteriorly  exerted,  which  slowly  but  surely  peels  the  ovary 
from  the  iliac.  It  is  possible  to  proceed  in  this  way  to  a  point  near  the 
posterior  side  of  the  adrenal.  If  one  attempts  to  go  farther  forward, 
hemorrhage  is  pretty  sure  to  result. 

The  next  step  is  to  attack  the  border  lying  over  the  adrenal.  This 
is  usually  easily  accomplished,  since  fear  of  injuring  the  adrenal  need 
not  stand  in  the  way,  though  rupture  of  the  adrenal  vein  is  to  be  avoided, 
since  the  blood  renders  further  proceedings  less  easy.  The  body  of 
the  ovary  is  freed  from  the  adrenal  around  the  anterior  end  and  down 
the  medial  edge,  peeling  the  ovary  from  its  attachments  toward  the 
iliac.  With  the  edges  of  the  ovary  freed  on  all  sides,  the  anterior  end 
is  peeled  back  until  less  than  a  fourth  of  its  length  remains  attached. 
From  this  point,  one  of  two  methods  may  be  followed.  The  anterior 
end  is  seized  with  the  forceps  and  the  whole  ovary  stripped  off,  the  line 
of  tension  being  as  nearly  parallel  to  the  surface  of  the  iliac  as  possible; 
or,  the  forceps  may  be  slipped  beneath  the  ovary  so  that  the  anterior 
and  posterior  ends  are  doubled  together  and  stripped  off  as  before.  If 
all  has  gone  exactly  right,  there  will  be  no  hemorrhage,  but  a  result  as 
completely  successful  as  this  is  rarely  obtained;  more  often  an  appar- 
ently fatal  hemorrhage  ensues.  If,  however,  a  bit  of  cotton  be  laid 
upon  the  site  of  the  ovary  and  the  bird  closed  up  as  if  all  were  well,  the 
hemorrhage  apparently  ceases,  for  such  birds  rarely  die,  though  they  do 
so  unless  cotton  is  inserted.  Autopsies  after  fatal  operations  show  that 
the  iliac  has  not  been  extensively  ruptured,  but  that  the  wall  has  been 
made  very  thin  or  even  broken  through  in  places.  The  blood-pressure 
at  this  point  is  so  low  that  the  cotton  is  sufficient  to  prevent  too  great 
a  loss  of  blood,  while  without  the  cotton  the  blood  continues  to  flow. 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS. 


13 


After  the  cotton  has  been  inserted,  all  that  is  necessary  is  to  close  the 
ribs  together  with  one  or  two  ties,  depending  on  the  size  of  the  bird. 
Finally,  the  skin  is  closed  with  a  continuous  suture.  It  is  not  necessary 
to  remove  suture  or  cotton  at  a  later  time,  as  they  apparently  never 
interfere  with  the  health  of  the  bird.  It  is  not  necessary  to  use  any 
but  the  most  ordinary  aseptic  methods. 

DESCRIPTION  OF  CASES. 
DUCKS. 

During  the  course  of  the  present  work,  females  and  males  have  been 
operated  on,  some  with  successful  results,  i.  e.,  complete  gonadectomy ; 
others  with  absolute  failure,  while  many  yielded  partially  successful 

TABLE  1. — Ovariotomized  female  ducks. 


Band 
No. 

No.  and  char- 
acter of  opera- 
tions. 

Date. 

Age  at 
first 
operation. 

Male 
charac- 
ters first 
noted. 

Results  and  remarks. 

f  Uncertain  

Mar.  11,  1909 

11  mos.  .  . 

July    4, 

Type  II.    Laying;  egg  in  ovi- 

4 

20 
24 

\Examination.  . 

Not   certainly 
complete. 
Uncertain  

Aug.  22,  1912 

Aug.  19,  1912 
Aug.  —  1909 

4  mos  .  .  . 
12  wks.  .  . 

1910 

Sept.  17 
July    4, 

duct  at  operation  ;  described 
in  Biol.   Bull.,    1910;   bird 
alive  Dec.  1915. 
Transitory  male  characters. 

Type  II.     Described  in  Biol. 

55 

58 
62 

Complete  
Complete  
Complete 

Aug.  20,  1912 
Aug.  20,  1912 
Aug.  20,  1912 

77  dys  .  .  . 
77dys..  . 
77  dys 

1910 
Sept.  14 
Sept.  14 
Sept.  14 

Bull.,  1910. 
Type  I  approximately. 
Type  II. 
Type  II. 

86 
116 
137 

Two;  both  in- 
complete. 
("Complete?  .... 
\Examination.  . 
f  Incomplete  
•j  Incomplete  .... 
[Examination 

Aug.  17,  1912 

Aug.     7,  1912 
Sept.    7,  1912 
June  13,  1912 
July  30,  1912 
Oct.    16,  1912 

About  63 
dys. 
11   to   12 
wks. 
About  10 
wks. 

Oct.    16 
Sept.  17 

No  male  characters. 
Type  II.     See  text. 
Transitory    male    characters. 
Ovary  found. 

138 

Incomplete.  .  .  . 

June  13,  1912 

No  male  characters. 

140 
169 

f  Complete  
i  Incomplete  
[Uncertain  
("Incomplete  
[Examination  .  . 

Aug.  15,  1912 
Aug.     9,  1912 
Oct.    16,  1912 
July  31,  1912 
Aug.  19,  1912 

About  10 
wks. 

45  dys.  .  . 

Sept.    4 
Sept.  14 

Transitory    male    characters. 
See  text. 

Type  I. 
No  ovary  found. 

173 

Probably  com- 
plete. 
Examination.  . 

July  30,  1912 
Aug.  19,  1912 

12  to   15 

wks. 

Sept.    4 

Type  I  approximately. 
No  ovary  found. 

174 
175 

Probably  com- 
plete. 
Examination.  . 
Two  ;    no    re- 

July 30,  1912 

Aug.  17,  1912 
July  31,  1912 

8  to  9  wks. 

Sept.    5 

Type  I  approximately.     See 
text. 

No  male  plumage. 

176 

moval      at- 
tempted. 
Complete  

Aug.     9,  1912 

Sept.    4 

Type  II.     Summer  plumage 

177 

182 

Complete  
Complete  

Aug.  10,  1912 
Oct.   31,  1912 

About  4| 
mos. 
4  wks  

Sept.    4 

unlike  winter  plumage. 
Probably  Type  I.    Died  Sept. 
1912. 
Type  I.     See  text. 

14  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

results.  These  last  throw  considerable  light  on  the  process  that  results 
from  the  removal  of  the  germ  glands.  Tables  1,  2,  and  3  give  a  sum- 
marized history  of  those  instances  that  yielded  pertinent  results.  In 
addition  to  these,  records  are  on  hand  of  a  considerable  number  of  other 
successful  experiments  made  at  the  Massachusetts  Experiment  Station. 
The  detailed  histories  of  several  cases,  selected  as  embodying  the  most 
important  results  of  the  work,  are  given  in  the  text. 

The  terminology  of  the  tables  requires  some  explanation.  The 
word  " character"  used  in  the  heading  of  the  second  column  refers  to 
the  nature  of  the  operation — i.  e.,  whether  the  removal  was  complete, 
partial,  or  otherwise,  as  well  as  could  be  determined  at  the  time.  It 
does  not  refer  to  the  actual  result  as  determined  by  the  later  history  of 
the  individual  in  question.  The  date  of  the  first  appearance  of  male 
characters  is  almost  always  that  of  a  feather  character  and  depends,  as 
stated  below,  upon  the  condition  of  the  plumage  at  the  time  of  the  oper- 
ation. In  many  instances  feathers  have  been  plucked  in  order  that 
the  change  might  be  more  readily  observed.  It  is  probable  that  the 
first  visible  change  often  occurs  earlier  than  stated,  but  no  attempt  was 
made  to  examine  the  birds  oftener  than  once  a  week.  The  number  of 
operations  on  each  bird  can  be  inferred  from  the  dates,  when  not  spe- 
cifically stated.  The  word  " examination"  means  that  the  bird  was 
opened  to  make  an  inspection  of  the  site  of  the  ovary.  The  word 
''approximately,"  used  in  connection  with  the  Type  I,  means  that  the 
individual  in  question  deviated  slightly  from  this  type  through  the 
presence  of  a  few  off-colored  feathers. 

FEMALE  DUCKS  COMPLETELY  OVARIOTOMIZED. 

No.  169.  This  bird  developed  as  perfect  a  coat  of  male  feathers  as 
has  appeared  on  a  castrated  duck,  though  others  equally  as  good  are 
now  available.  She  is  shown  in  plate  in.  Hatched  June  16,  she  was  a 
little  over  6  weeks  of  age  when  operated  on,  July  31.  A  photograph 
taken  a  few  days  after  the  operation  (plate  vn,  D,  foreground)  shows 
that  the  bird  was  still  in  the  down  and  had  not  yet  begun  to  develop 
the  first  coat  of  definitive  feathers.  Although  the  protocol  states, 
among  other  things,  that  "  removal  was  probably  not  quite  complete," 
the  results  show  that  actually  the  removal  was  complete. 

On  August  19,  a  second  operation  was  made,  its  object  being  an 
inspection  of  the  site  of  the  ovary.  The  protocol  states : 

"A  thorough  and  careful  examination  failed  to  show  any  trace  of  an  ovary. 
However,  to  make  assurance  doubly  sure,  all  the  connective  tissue  on  the 
site  of  the  ovary  was  removed,  except  a  little  on  the  spot  where  the  rent  in 
the  vena  cava  is  apt  to  occur.  As  this  could  not  be  removed  without  danger 
to  the  vena  cava,  this  spot  was  seared." 

On  September  5,  it  was  noted  that  the  juvenile  plumage  was  like 
that  of  the  young  female,  except  the  dorsal  surface  of  the  wings,  some 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  15 

of  the  feathers  of  this  region  being  male-like,  i.  e.,  they  lacked  the 
brownish  margin  characteristic  of  the  female. 

On  September  14  the  first  male  characters,  as  indicated  by  the  mark- 
ings and  color  of  the  plumage,  had  begun  to  appear.  Later  in  the 
year,  when  the  juvenile  to  adult  molt  was  completed,  the  bird  had 
essentially  the  same  appearance  as  that  given  in  the  plate.  Since  that 
time  there  has  been  no  change  in  the  character  of  the  bird,  though  she 
has  molted  several  times. 

The  bird,  however,  is  not  entirely  a  replica  of  a  male.  If  the 
mandible  be  compared  with  that  of  the  drake  in  plate  i  it  will  be 
observed  that  they  are  quite  unlike.  That  of  the  male  is  typical 
for  his  sex,  while  that  of  No.  169  is  typical  for  the  castrated  female 
and  resembles  that  of  the  female.  It  differs  from  that  of  the  nor- 
mal female,  plate  11,  in  having  the  dark-greenish  patches,  mostly 
marginal,  replaced  by  a  clean  yellow,  or,  to  put  the  matter  a  little 
differently,  the  black  area  of  the  normal  female  was  not  affected  by 
castration,  but  the  dull  greenish-yellow  pigment  did  not  develop.  An 
explanation  of  this  failure  possibly  lies  in  the  age  at  which  the  black 
pigment  becomes  fixed.  When  first  hatched,  Rouen  ducklings  and 
many  hybrids  have  bills  that  are  almost  black.  In  ducklings  a  month 
old  the  sexual  differentiation  of  the  mandible  color  toward  that  of  the 
adult  has  already  begun.  In  the  male  the  colors  gradually  lighten  until 
they  reach  the  adult  condition.  In  the  normal  females,  however,  very 
little  apparent  change  takes  place  in  the  region  where  the  blotch  of 
the  adult  is  located.  The  margins,  however,  gradually  change  to  the 
color  of  the  adult.  A  further  discussion  concerning  this  change  will 
be  found  in  a  later  section.  It  is  possible,  however,  that  something 
very  different  actually  occurs.  It  may  be  that  the  black  pigmentation 
of  the  mandible  of  the  ducklings  is  a  juvenile  condition,  and  that  in 
each  sex  this  disappears,  leaving  an  underlying  condition  which  it  has 
concealed. 

No.  182.  The  history  of  this  individual  contains  several  features  of 
particular  interest.  In  the  first  place,  the  operation  was  performed 
when  the  bird  was  4  weeks  of  age.  She  is  one  of  the  youngest  ducks 
from  which  the  ovary  has  been  entirely  removed.  Hatched  October  1, 
of  non-pedigreed  ancestry,  the  operation  was  performed  October  31. 
Later  developments  show  that  the  duck  was  of  the  " plain  head"  type 
described  in  an  earlier  paper.  The  juvenile  coat  (i.  e.,  first  coat  of 
definitive  feathers)  was  not  distinguishable  from  that  of  the  normal 
female.  Owing,  perhaps,  to  the  unfavorable  conditions  under  which 
it  was  necessary  to  keep  the  duckling  during  her  first  winter,  she  grew 
very  slowly  and  did  not  attain  the  adult  plumage  that  winter.  In 
March  she  again  came  under  the  immediate  care  of  the  writer  and  was 
given  special  attention.  The  more  favorable  conditions  following  on 
the  long  period  of  adverse  environment  apparently  induced  a  molt,  for 


16  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

the  bird  soon  lost  the  juvenile  coat  and  developed  the  adult  coat  of  the 
male  of  this  variety,  which  has  a  silver-gray  breast  (sometimes  slightly- 
tinged  with  purple)  instead  of  the  ruddy  breast  of  the  mallard,  though 
the  other  secondary  sexual  characters  are  the  same.  The  new  coat  of 
the  duck  was  imperfect  in  many  respects,  but  there  was  not  the  slight- 
est doubt  of  its  general  character.  No  sooner  had  the  feathers  of  this 
coat  become  fully  mature  than  it  was  lost,  being  replaced  by  a  coat  like 
that  of  the  summer  coat  of  the  male  of  this  variety.  That  it  was  neither 
a  juvenile  nor  female  coat  is  shown  by  two  things:  First,  a  few  feathers 
were  vermiculated,  a  characteristic  of  the  male's  summer  coat;  second, 
this  coat  was  replaced  early  in  the  autumn  by  the  typical  male  plumage 
of  this  variety.  In  the  summers  of  1914  and  1915  the  change  to  the 
summer  plumage  was  followed  by  a  return  to  the  breeding  plumage 
in  the  fall. 

Besides  being  the  first  instance  of  the  clear  assumption  of  the  summer 
plumage  of  the  male  by  a  castrated  female,  this  bird  is  interesting  in 
another  point,  i.  e.  she  has  never  developed  a  good  duck's  voice.  As 
already  pointed  out,  only  the  female  gives  voice  to  the  familiar  sono- 
rous quack.  The  drake  never  quacks,  but  produces  a  sound  that  can 
best  be  described  as  a  whispered  "qua."  No.  182  has  never  been  able 
to  produce  anything  more  than  a  broken  quack,  a  sound  best  described 
as  intermediate  between  that  of  the  male  and  female,  except  when 
handled  or  otherwise  subjected  to  special  stimulus.  Ordinarily  she 
simply  whispers  "qua,  qua,"  very  much  as  the  drake  does. 

In  two  respects,  then,  viz,  assumption  of  summer  plumage  and  im- 
perfect voice,  this  individual  approaches  more  closely  to  the  male  than 
any  bird  previously  operated  on.  Both  the  site  of  the  ovary  and  the 
corresponding  region  on  the  right  side  were  examined  in  the  autumn 
of  1915  by  means  of  an  operation.  They  were  entirely  empty. 

Nos.  4  and  116.  These  two  have  been  selected  for  description  because 
they  represent  a  different  and  important  type  of  result  following  removal 
of  the  ovary.  In  addition,  No.  4  is  the  oldest  female  from  which  an 
ovary  has  been  successfully  removed.  As  she  has  been  described 
rather  fully  in  an  earlier  paper,  only  a  brief  summary  of  the  case  will  be 
given  here.  The  first  operation  was  made  when  the  bird  was  nearly  a 
year  old.  She  was  laying  regularly  immediately  previous  to  the  opera- 
tion and  in  its  course  an  egg  with  shell  membranes  fully  formed 
was  removed  from  the  oviduct.  The  anterior  half  of  the  latter  was 
also  removed.  By  means  of  a  second  operation,  August  22,  1912,  it 
was  ascertained  that  no  trace  of  the  ovary  was  present  on  the  left  side, 
nor  as  far  as  could  be  determined  on  the  right,  though  a  thorough  ex- 
amination of  this  side  was  impossible  from  the  opening  made  on  the 
left.  The  bird  is  alive  at  date  of  writing,  December  3,  1915.  The 
development  of  male  characters  has  been  very  slight  as  compared  to 
the  cases  just  described.  She  is  clearly  in  an  intermediate  condition, 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  17 

approaching  more  closely  to  the  female  than  to  the  male  in  general 
color.  However,  since  her  feather  coloring  resembles  neither  the  nor- 
mal female  nor  the  male  in  breeding  plumage,  it  is  perhaps  better  to 
consider  this  bird  as  a  distinct  type,  designated  below  as  Type  II 
(plate  iv).  The  majority  of  her  individual  feathers  are  either  male  or 
female  in  character  and  not  a  mixture  of  the  two.  The  plumage  as  a 
whole,  however,  is  a  mixture,  containing  typical  male  and  female 
feathers,  plus  a  third  type  that  is  neither.  The  latter  are  brown  and 
buff,  but  are  barred  transversely,  either  in  a  perfect  or  more  or  less 
broken  pattern  (plate  vi,  figs,  r  and  q).  On  the  ventral  surface  some 
feathers  are  more  or  less  intermediate — i.  e.,  each  feather  shows  both 
male  and  female  characters.  On  the  whole  the  condition  approaches 
most  nearly  to  that  of  the  male  in  his  summer  plumage,  but  differs 
enough  so  that  it  can  not  be  said  that  it  is  such  a  plumage,  especially 
in  this  individual,  which  is  very  much  more  like  an  unaltered  female 
than  the  bird  figured.  Further,  this  plumage  is  maintained  through- 
out the  year. 

No.  116,  a  pure-bred  Rouen,  belongs  to  the  same  type  as  No.  4. 
Hatched  May  18,  1912,  the  ovary  was  removed  August  7,  1912,  the 
removal  being  complete  as  far  as  an  examination  with  the  naked  eye 
could  determine.  She  was  examined  from  time  to  time  and  no  male 
feathers  were  found  as  late  as  September  7.  Accordingly,  the  bird  was 
opened  and  a  careful  examination  made  of  the  left  side.  No  trace  of 
any  ovarian  material  could  be  found.  The  lack  of  male  feathers  a 
month  after  the  operation  was  probably  due  to  the  fact  that  it  was  not 
ready  to  exchange  the  juvenile  coat  for  the  adult.  Thus  the  feathers 
regenerating  from  follicles  emptied  at  the  time  of  operation  belonged  to 
the  juvenile  plumage.  By  October  26  the  juvenile  had  been  replaced 
by  the  adult  plumage,  which  belonged  to  the  type  described  for  No.  4. 
The  further  history  of  the  case  is  complicated  by  an  attempt  to  engraft 
bits  of  ovary  beneath  the  skin.  Apparently,  however,  the  implanted 
ovary  was  without  influence,  for  feathers  plucked  at  the  time  were 
replaced  a  month  later  by  either  typical  male  feathers  or  those  of 
Type  II.  For  a  time  the  bird  was  not  under  observation,  but  in  the 
spring  of  1913  she  had  not  changed  in  any  essential.  This  condition 
was  maintained  throughout  the  summer,  until  the  fall  molt  took  place, 
when  to  my  surprise  she  developed  a  much  more  perfect  male  coat, 
corresponding  closely  to  that  shown  in  plate  iv,  which  is  a  figure  of 
No.  24  described  in  an  earlier  paper.  A  discussion  of  this  type  will  be 
taken  up  in  a  later  section. 

FEMALE  DUCKS  PARTIALLY  OVARIOTOMIZED. 

We  may  now  turn  our  attention  to  some  of  the  cases  in  which  the 
removal  of  the  ovary  was  almost  but  not  quite  complete.  These  cases 
throw  considerable  light  on  the  effects  of  removal,  besides  giving  us  a 
more  precise  knowledge  of  the  action  of  the  ovarian  secretion. 


18  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

No.  140.  The  first  operation  was  made  June  15,  1913.  The  exact 
age  of  the  bird  was  unknown,  as  the  original  band  had  been  lost,  but 
she  was  approximately  3  months  old.  The  ovary  was  apparently 
completely  removed  without  hemorrhage.  The  apparently  complete 
removal  was  demonstrated  to  members  of  the  staff  of  the  Station  for 
Experimental  Evolution  at  Cold  Spring  Harbor.  Several  weeks  after 
the  operation  the  bird  had  not  developed  any  trace  of  male  plumage. 
Accordingly,  August  9,  she  was  operated  upon  again.  Lying  over  the 
suprarenal  was  a  considerable  mass  of  ovarian  tissue,  in  addition  to  a 
minute  piece  farther  back.  Both  pieces  were  removed.  By  September 
7  new  feathers  had  replaced  those  that  were  pulled  at  the  time  of  the 
operation.  The  distal  portions  of  the  new  feathers  were  female,  the  more 
proximal  giving  evidence  of  the  absence  of  the  influence  of  the  ovary 
by  transverse  vermiculations,  which,  however,  were  brownish.  By 
October  16  male  feathers  were  present  in  various  portions  of  the  body. 
However,  the  younger  feathers  that  were  growing  at  this  time  were 
entirely  female  in  character,  indicating  that  some  change  had  taken 
place.  This  led  to  a  re-examination  of  the  site  of  the  ovary.  This  was 
empty,  but  attached  to  the  mesenteries  was  a  bit  of  ovary,  the  size  of 
a  small  pea,  while  attached  to  the  oblique  septum  on  the  left  side  was 
a  bit  of  ovary  containing  one  macroscopic  ovum.  Both  were  removed. 
However,  no  further  progress  was  made  in  assuming  male  characters. 
The  bird  was  kept  until  June  21,1913,  when  she  was  killed  and  exam- 
ined. The  oviduct  was  infantile,  except  that  the  walls  of  the  vaginal 
region  were  somewhat  thickened  and  corrugated.  On  the  site  of  the 
ovary  was  a  single  small  object  like  an  immature  ovum,  about  1  mm.  in 
diameter.  On  the  right  side  was  a  body  5  or  6  mm.  in  diameter  bearing 
(partially  embedded)  two  small  vesicles  filled  with  a  deep-yellow  serous 
fluid.  This  body  has  not  yet  been  examined  histologically.  Evidently, 
then,  from  the  history  of  this  bird  we  may  conclude  that  a  very  small 
amount  of  ovarian  tissue  is  sufficient  to  produce  normal  female  char- 
acters. There  is  a  point,  however,  at  which,  either  because  the  amount 
of  tissue  is  so  small  or  possibly  because  of  injury  received  during  the 
operation,  the  fragment  of  ovary  no  longer  suffices  to  produce  female 
secondary  sex  characters.  Similar  results  have  been  obtained  in  other 
cases,  as,  for  example,  Nos.  20  and  137. 

MALE  DUCKS  COMPLETELY  ORCHIDOTOMIZED. 

The  results  of  castration  of  drakes,  as  far  as  investigated,  appear  to 
be  independent  of  age.  Much,  however,  clearly  depends  on  the  com- 
pleteness of  the  removal  and,  less  clearly,  on  the  nature  of  the  material 
left  behind.  The  testicles  are  not  always  readily  removed,  because 
in  early  stages  they  are  cylindrical  objects,  pointed  at  each  end  and 
attached  along  one  side  to  the  iliac.  In  ducks,  the  elongated  condi- 
tion is  maintained  much  longer  than  in  fowl.  In  either  case,  if  the 
correct  procedure  is  followed,  it  is  possible  to  remove  the  testicles  com- 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS. 


19 


pletely,  even  when  in  the  elongated  condition;  though  it  frequently 
happens  that,  owing  to  the  extremely  fragile  nature  of  the  testes, 
they  become  broken.  When  this  happens  it  is  difficult  to  make  sure 
that  all  testicular  material  is  removed;  that  left  behind  is  very  apt  to 
grow.  A  second  difficulty  arises  because  of  the  relation  of  the  sperma- 
togenic  portion  of  the  testes  to  the  ducts.  The  Wolffian  body  lies  upon 
the  surface  of  the  iliac  and  in  intimate  union  with  it.  In  removing  the 
testes  from  young  birds  this  is  usually  left  behind,  and  in  some  instances 
it  apparently  develops  independently  of  the  spermatogenic  portion. 
In  a  few  instances  birds  have  been  subjected  to  autopsy  without 
finding  any  trace  of  testicular  material.  Further  work  is  required  on 
this  point,  since,  naturally,  these  facts  have  been  learned  as  the  work 
has  progressed. 

TABLE  2. — Orchidotomized  male  ducks. 


Band 
No. 

No.  and  character 
of  operations. 

Date. 

Age  at 
operation. 

Results  and  remarks. 

1 

Left  removed  right 

Aug     8  1909 

15  mos 

Did  not  assume  summer  plu- 

19 

ligatured  and  left 
in  situ. 

Right  only  removed 

Mar.  11,  1909 

1  1  mos  

mage  in   1910,    1911,    1912, 
1913,  or  1914.     In  summer 
plumage  when  operated  on. 
See  text. 
Summer  plumage  in  1909. 

470 
119 

Complete  
Left  only  

Mar.  11,  1909 
Aug.     9,  1912 

11  mos  
11  to  12  wks.. 

Did  not  assume  summer  plu- 
mage in  1909  nor  during  the 
remainder  of  his  life. 
Summer  plumage.    See  text. 

136 

Left  removed  

June  13,  1912 

About  10  wks  . 

Assumed     summer     plumage 

143 

Both  removed 

Aug.     7,  1912 

51  dys  

1913.     See  text. 
No  summer  plumage.    See  text. 

170 

Complete  

July  31,  1912 

45  dys  

No  summer  plumage. 

171 

Complete  

July  31,  1912 

45  dys  

No  summer  plumage.    See  text. 

172 
186 

Not  certainly  com- 
plete. 
Both  removed 

June  29,  1912 
Oct.    31,  1912 

10  to  15  wks.. 
4  wks  

Summer  plumage.     See  text. 
Did  not  assume  summer  plu- 

mage 1913.    See  text. 

No.  1 .  This  bird  was  over  a  year  old  when  operated  upon,  August  8, 
1909.  He  was  in  full  summer  plumage  at  the  time.  The  left  testis 
was  removed.  A  ligature  was  placed  tightly  about  the  base  of  the 
right  testis  and  this  testis  was  allowed  to  remain.  This  bird  did  not 
assume  the  summer  plumage  in  1910, 1911, 1912, 1913,  or  1914.  He  was 
killed  in  December  1914.  No  trace  of  testicular  material  could  be  found. 
Traces,  however,  of  the  vas  deferens  were  found  near  its  anterior  end. 

No.  171.  This  bird,  a  few  days  after  the  operation,  is  shown  in 
plate  vii,  D,  rear;  hatched  June  16,  the  testes  were  removed  July  31, 
1913.  The  protocol  states  that  removal  was  complete  but  in  fragments. 
The  laterals  and  scapulars  were  just  beginning  to  appear.  The  history 
of  this  bird  was  exactly  that  of  a  normal  one  to  the  time  for  the  summer 
molt.  June  10,  1913,  the  bird  was  molting,  but  the  new  feathers  were 
exactly  like  the  old,  i.  e.}  the  bird  did  not  develop  the  summer  plumage 
of  the  normal  male. 


20  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

No.  186.  The  history  of  this  bird  is  similar  to  the  preceding.  The 
testes  were  completely  removed  when  the  bird  was  4  weeks  of  age.  In 
1913,  1914,  and  1915  the  bird  molted  but  did  not  assume  the  summer 
plumage.  At  autopsy  no  trace  of  the  testes  could  be  found.  It  is  of 
some  interest  to  note  that  the  molt  took  place  at  the  same  time  of  year 
in  1913  as  that  of  No.  171,  though  No.  186  was  3|  months  younger. 

MALE  DUCKS  PARTIALLY  ORCHIDOTOMIZED. 

The  history  of  the  cases  where  the  removal  of  the  testes,  intention- 
ally or  otherwise,  was  incomplete  may  be  considered  here  in  condensed 
form. 

No.  119.  August  9,  19l2,  the  left  testis  was  removed.  June  10, 
1913,  the  bird  was  found  to  be  assuming  the  summer  plumage.  July 
10,  when  the  bird  was  in  full  summer  plumage,  he  was  killed.  On  the 
left  was  some  testicular  material.  The  vas  deferens  of  this  side  was 
small  and  straight  and  scarcely  visible.  On  the  right  was  an  immense 
testis,  fully  twice  the  size  of  that  of  a  normal  male.  The  vas  deferens 
was  convoluted  and  contained  semen,  but  was  not  as  large  as  usual. 
Penis  and  syrinx  were  normal. 

No.  136.  Left  testis  removed  in  several  pieces,  June  13,  1912.  On 
July  1, 1913,  the  bird  was  killed  while  in  full  summer  plumage.  Vasa 
deferentia  small,  not  easily  seen.  On  the  left  was  a  small  testis  about  a 
third  the  diameter  of  a  normal  testis,  but  of  full  length  and  irregular  in 
shape.  The  right  testis  was  normal,  though  a  little  irregular  in  shape. 

No.  172.  The  testes  were  removed  June  29,  1912.  The  epididymi 
were  probably  left  behind,  nor  was  it  certain  that  all  testicular  material 
was  entirely  removed,  though  the  sites  of  the  testes  were  carefully  wip  ed 
off.  Whatever  testicular  material  was  left  behind  was  not  visible  to 
the  naked  eye.  June  10,  1913,  the  bird  began  to  molt  and  to  assume 
the  summer  plumage.  August  10,  when  in  full  summer  plumage,  he 
was  killed  and  dissected.  On  the  site  of  each  testis  was  a  relatively 
small  amount  of  testicular-like  material  containing  numerous  vesicles 
of  approximately  equal  size  filled  with  a  yellowish  fluid.  The  vasa 
deferentia  were  found  with  difficulty.  They  were  very  infantile  and 
non-convoluted.  The  penis  was  rather  small  and  contained  only  a 
little  mucus. 

It  is  perfectly  evident  that  the  male  after  castration  often  does  not 
assume  the  summer  plumage,  but  a  number  of  points  remain  to  be 
cleared  up.  While  the  sites  of  the  testes  have  been  found  entirely 
empty  in  several  instances  where  the  summer  plumage  has  not  been 
assumed,  there  are  also  several  cases  where  material  has  been  found  at 
autopsy  on  the  site  of  the  testes.  While  the  histological  examination 
of  this  material  is  not  yet  complete,  it  is  probably  not  spermatogenic. 
On  the  other  hand,  where  the  males  have  assumed  the  summer  plumage 
after  castration,  material  that  looks  much  like  that  just  noted  is  always 
found.  In  several  such  instances,  seminal  tubules  with  spermatozoa 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS. 


21 


have  been  found.  It  has  seemed  best,  however,  not  to  delay  the  rest 
of  the  paper  to  complete  the  histological  work,  especially  as  similar 
material  has  been  found  in  castrated  females  (fowl)1  and  as  a  number  of 
the  birds  are  still  under  observation.  It  seems  probable  that  the  body 
found  is  the  epididymis,  which  has  developed  in  the  absence  of  both 
germ  cells  and  supporting  cells. 

DOMESTIC  FOWL. 

The  operations  on  fowl  yield  results  similar  to  those  from  ducks. 
The  latter  thus  far  have  proved  more  suitable  for  experimentation 
because  of  greater  hardiness  and  freedom  from  diseases,  at  least  in  the 
stocks  available.  Moreover,  the  ovary  is  removed  more  readily  than 
from  chicks.  For  these  reasons  fewer  cases  are  available  for  the  fowls 
than  for  ducks. 

TABLE  3. — Ovariotomized  female  fowl. 


Band 
No. 

No.  and  char- 
acter of  opera- 
tions. 

Date. 

Age.  at  first 
operation. 

Male 
characters 
first 
noted. 

Results  and  remarks. 

1193 

Mar.  31,  1911 

4  wks  

Transitory  male  plumage. 

Described     in     Amer. 

Naturalist,  1913. 

1196 

Mar.  31,  1911 

4  wks          .    . 

Male  plumage.  Described 

in    Amer.    Naturalist, 

1913.     See  text. 

(Transitory.2     Spurs    de- 

4042 

f  Complete  

Sept.    7,  1912 

\ 

1     veloped    well.      Killed 

\Examination.  . 

Dec.  14,  1912 

/" 

|     Oct.  10,  1913.     Ovary 

[     regenerated. 

4050 

(Incomplete  
\Examination.  . 

Sept.    6,  1912 
Dec.  14,  1912 

>  About  3  mos  . 

Sept.  19 

("Transitory.2     Ovary    re- 
\     generated. 

4071 

Complete  

Sept.    6,  1912 

About  3  mos  . 

Sept.  19 

Transitory.2 

4140 

flncomplete  
\Examination.  . 

Sept.    6,  1912 
Dec.  14,  1912 

>  About  4  mos  . 

Sept.  22 

(New  feathers  completely 
j     male.      Died   Aug.    1, 
[     1913.     See  text. 

4154 

Partial  

Sept.    7,  1912 

Sept.  26 

Transitory.2  Oct.  12  ovary 

found. 

4288 

Complete  

Sept.    4,  1912 

32  dys  

Sept.  26 

Transitory.2    Killed  June 

11,  1913. 

4290 

Complete  

Sept.    1,  1912 

32dys  

Sept.  21 

Good  male.    See  text. 

4470 

Possibly  com- 

Nov. 13,  1912 

66  dys    .  .  . 

Nov.  26 

Transitory.2 

plete. 

4471 

Complete  

Nov.  13,  1912 

66  dys 

Nov.  26 

Good  male.    See  text. 

FEMALE  FOWL  COMPLETELY  OVARIOTOMIZED. 

No.  4471-  Hatched  September  8,  1912.  According  to  the  protocol 
made  November  13, 1912,  "a  clean  and  complete  removal  of  the  ovary 
was  effected. "  By  November  26,  male  characters  in  the  form  of  black 
feathers  were  visible  in  the  breast.  These  continued  to  increase  in 


lCf.  Goodale,  1916. 


2Male  plumage. 


22  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

numbers  with  the  age  of  the  bird  until  a  complete  juvenile  plumage  was 
developed,  this  being  replaced  in  turn  by  an  imperfect  adult  male  coat". 
(It  should  be  noted  that  in  many  males  of  the  strain  used,  the  full  adult 
plumage,  particularly  in  late-hatched  individuals,  may  not  appear 
until  after  the  molt  of  the  second  season.)  After  the  annual  molt,  the 
plumage  had  reached  the  adult  condition.  Plate  v  is  from  a  painting 
of  the  bird  made  in  1913,  when  it  was  about  1|  years  of  age. 

Certain  points  call  for  further  comment.  First,  the  plumage,  partic- 
ularly in  proportion  to  the  size  of  the  bird,  is  more  like  that  of  the 
capon  than  that  of  the  cock — i.  e.,  the  feathers  are  longer.  Second, 
the  head  is  small  and  in  the  absence  of  a  good-sized  comb  appears  even 
smaller.  Third,  the  bird  as  a  whole  is  small,  approximating  the  hen 
in  size.  Fourth,  the  shanks  are  comparatively  short  and  of  relatively 
delicate  build,  giving  the  bird  a  low-set  appearance.  Although  the 
spurs  are  well  developed,  the  legs  are  those  of  a  hen  and  not  those  of  the 
cock  or  capon. 

The  history  of  this  bird  during  the  summer  of  1914  is  of  partic- 
ular interest.  It  was  observed  that  it  molted  in  early  summer  and 
that  the  new  coat  was  quite  different  from  the  old.  The  breast 
became  suffused  with  red,  because  the  new  feathers  were  red  and  black, 
resembling  strongly  those  of  the  young  male.  The  dorsal  regions  lost 
their  bright  appearance  and  became  relatively  dull-colored.  The 
individual  feathers  of  the  saddle  were  relatively  short  with  rounded 
ends,  and  were  stippled  brownish  red  on  a  black  ground.  They  were 
not  colored  like  those  of  the  female,  though  they  had  the  shape  of  hen 
feathers.  The  distal  portion  of  the  feathers  of  the  wing  bow  became 
black  and  red,  instead  of  red  alone,  while  the  barbuleless  margins  dis- 
appeared. The  secondary  coverts  became  red  and  black  instead  of 
uniform  black.  These  statements  are  sufficient  to  illustrate  the  char- 
acter of  the  more  important  changes.  By  late  August,  however,  the 
new  feathers  coming  in  were  again  completely  normal  male  in  char- 
acter, and  by  early  October  the  bird  was  well  on  its  way  toward  the 
reassumption  of  the  completely  normal  male  plumage,  which  has  been 
maintained  ever  since.  It  has  been  determined  by  an  operation  that 
no  ovary  was  present,  though  an  organ  of  an  entirely  different  histo- 
logical  structure  was  found.  (See  page  24.) 

No.  4290  is  in  many  respects  a  parallel  case  to  4471,  although  some- 
what older  and  castrated  earlier  in  the  year.  Her  history  subsequent 
to  castration  and  up  to  the  time  4471  began  to  molt  is  the  same.  This 
bird  underwent  the  usual  molt,  but  showed  only  male  feathers  until 
killed  late  in  November  1914. 

As  in  the  ducks,  several  instances  have  been  observed  where  the 
assumption  of  male  plumage  was  not  complete,  many  of  the  feathers 
being  in  an  intermediate  condition,  although  the  birds  were  com- 
pletely castrated,  as  shown  by  autopsy  or  operation.  One  instance  is 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  23 

No.  1196,  whose  history  has  already  been  briefly  given  in  the  American 
Naturalist,  but  which  it  may  be  well  to  give  in  more  detail.  The  bird 
was  purchased  as  a  day-old  chick  from  a  breeder.  The  chicks  of  the 
lot  of  which  this  was  a  member  were  exceptionally  strong  and  vigorous. 
This  individual  was  first  opened  when  10  days  old  and  a  part  of  the 
ovary  removed,  but  a  hemorrhage  started,  so  the  operation  was  discon- 
tinued and  the  opening  closed.  Ten  days  later  she  was  again  opened 
and  the  remainder  of  the  ovary  removed  with  great  ease  and  without 
hemorrhage.  At  the  time  of  the  second  operation  the  chick  was  in  the 
down  except  for  the  remiges  and  rectrices.  The  chick  plumage  (see 
page  9)  began  to  come  in  soon  after  this.  As  this  plumage  is  alike  in 
the  two  sexes,  no  evidence  of  any  results  appeared  until  the  juvenile 
plumage  began  to  develop.  From  this  time  on,  the  bird  exhibited  the 
characters  of  the  male  except  that  the  comb  and  wattles  grew  less  rap- 
idly than  is  the  case  in  most  normal  males  of  this  variety.  At  6  months 
of  age,  while  larger  than  those  of  the  check  pullets,  these  appendages 
were  distinctly  female  in  form  and  shape.  Eventually  they  became  equal 
in  size  and  shape  to  those  of  many  cocks.  Unfortunately,  the  males  that 
had  been  kept  as  checks  on  the  rate  of  comb-growth  disappeared,  prob- 
ably taken  by  rats;  but  even  if  they  had  not  been  lost,  the  com- 
parison would  have  been  of  small  value,  since  the  normal  variation  in 
rate  of  comb-growth  is  so  large.  In  due  course  of  time  the  juvenile 
plumage  was  replaced  by  that  of  the  adult  male,  though  differing  in  two 
points:  first,  the  sickles  of  the  tail  were  missing;  secondly,  many  of  the 
feathers  of  the  saddle  region  were  not  long,  pointed,  and  golden-laced 
with  black  stripes,  but  were  broad,  rounded  at  the  ends,  and  colored 
dark  brown  with  minute  red  spots  or  stippling  (fig.  c,  American  Nat- 
uralist, 1913).  In  shape  and  size  they  were  identical  with  those  of  the 
hen,  but  the  coloring  differed,  being  more  like  similar  feathers  found  in 
this  region  in  the  juvenile  plumage  of  the  male.  The  bird  was  kept 
until  she  was  well  into  the  molt  of  the  second  year,  in  hopes  that  these 
would  be  replaced  by  typical  male  saddle  feathers.  Nothing  of  the 
sort  happened.  Each  kind  of  feather  was  replaced  by  one  of  the 
same  kind.  In  other  words,  no  further  development  of  the  plumage 
toward  the  male  type  occurred.  In  the  light  of  other  observations,  it 
is  probable  that  even  if  the  bird  had  not  been  killed  at  this  time  she 
would  not  have  developed  more  of  the  male  plumage. 

The  non-development  of  the  sickle  feathers  of  the  tail  may  be 
explained  in  the  following  manner :  The  dorsal  part  of  the  uropygium 
was  missing,  resulting  in  a  deficiency  in  the  number  of  rectrices,  there 
being  only  8  instead  of  the  usual  12  or  14.  The  oil  gland  also  was  miss- 
ing. Moreover,  a  rumpless  cock  appeared  in  a  younger  brood  obtained 
from  the  same  breeder.  Correspondence  brought  the  fact  that  such 
birds  occasionally  appeared  in  his  home  flock.  The  evidence,  then, 
indicates  that  the  deficiency  in  sickles  and  tail  feathers  had  nothing 


24  GONADECTOMY   IN    RELATION   TO   THE    SECONDARY 

whatsoever  to  do  with  the  absence  of  the  ovary,  but  was  purely  a  coin- 
cidence. 

The  findings  at  autopsy,  illustrated  by  fig.  C,  plate  vn,  are  of  par- 
ticular interest.  On  the  site  of  each  germ  gland  was  a  mass  of  whitish 
tissue,  and  leading  from  it  to  the  cloaca  was  a  slightly  convoluted  tubule. 
On  the  left  was  a  distinct  but  infantile  oviduct.  No  trace  of  one  could 
be  found  on  the  right.  On  the  right "  gonad  "  were  several  vesicles  filled 
with  a  rather  thick  but  clear  yellow  fluid.  Sections  of  these  "gonads" 
showed  a  compact  mass  of  small  cells  having  a  large  nucleus  in  propor- 
tion to  the  protoplasm.  The  whole  mass  suggested  nothing  so  much  as 
early  nephrogenous  tissue.  There  was  not  the  slightest  trace  of  seminal 
tubules  nor  of  spermatozoa,  nor  was  there  any  trace  of  degeneration. 
According  to  Foges  and  others,  transplanted  testicular  tissue  always 
contains  seminal  tubules  and  spermatozoa.  It  seems  probable,  then, 
that  after  the  removal  of  the  ovary  the  Wolffian  body  and  ducts  under- 
went a  compensatory  development.  It  is  well  known,  of  course,  that 
the  right  ovary  degenerates  in  female  birds  and  that  in  the  male  the 
Mtillerian  ducts  disappear;  but,  according  to  Lillie,  nothing  is  known 
of  the  fate  of  the  Wolffian  ducts  in  the  female. 

The  hermaphroditic  condition  of  the  accessory  organs  of  reproduc- 
tion in  this  individual  led  to  a  search  for  similar  organs  in  normal  females. 
In  some  individuals  it  is  comparatively  easy  to  demonstrate  on  the 
right  side  a  small  amount  of  tissue  that  may  be  interpreted  either  as 
the  degenerated  gonad  or  the  remnants  of  the  Wolffian  body  of  this 
side.  Leading  from  this  is  a  strand  of  tissue  which  can  be  interpreted 
as  the  Wolffian  duct.  In  most  females  it  is  impossible  to  demonstrate 
these  traces,  but  several  young  normal  females  have  been  found  in 
which  there  can  be  no  doubt  of  the  existence  of  these  structures. 
Whether  or  not  they  are  really  the  rudiments  of  the  Wolffian  body  and 
ducts  remains  to  be  determined.  On  the  left  it  is  almost  impossible 
to  find  traces  of  the  " Wolffian  body,"  but  the  "duct"  can  sometimes 
be  found.  A  further  investigation  of  these  structures  is  being  made 
in  the  hope  that  their  nature  may  be  definitely  determined. 

If  the  observations  of  Beard  and  Allen  regarding  the  original  source 
of  the  germ  cells  in  the  endoderm  are  correct,  and  if  Ancel  and  Bouin 
are  correct  in  referring  the  production  of  the  internal  secretion  of  the 
testes  to  the  interstitial  cells,  the  degree  of  comb  development  may  be 
referred  to  them  rather  than  the  germ  cells.  To  determine  this  point 
involves  considerable  histological  work  which  as  yet  it  has  been  impos- 
sible to  accomplish.  In  the  present  instance  we  have  had  a  large  comb 
develop  on  a  bird  in  the  absence  of  the  germ  cells  proper.  Of  course, 
it  is  possible  that  some  of  the  cells  of  the  glandular  mass  may  have 
been  potential  germ  cells,  but  there  is  no  evidence  that  such  is  the 
case.  On  the  other  hand,  the  large  comb  and  wattles  developed 


SEXUAL    CHARACTERS   OF   SOME   DOMESTIC    BIRDS.  25 

slowly,  probably  accompanied  by  the  development  of  the  "Wolffian 
body"  pari  passu.  A  further  discussion  can  best  await  the  results  of 
the  examination  of  several  other  instances  of  similar  nature  now  on 
hand. 

No.  2058.  This  bird  is  of  considerable  interest.  She  is  a  pure-bred 
Brown  Leghorn  from  the  stock  of  one  of  the  best-known  breeders  of 
the  variety  in  this  country.  She  was  2  months  of  age  when  the 
ovary  was  removed.  In  2  weeks  the  first  male  feathers  had  begun  to 
appear.  The  development  of  male  characters  continued  until  late  in  the 
fall,  when  she  was  a  very  good  young  male  in  appearance.  As  stated 
above,  young  males  and  castrated  females  under  some  circumstances 
are  slow  in  reaching  a  complete  development  of  the  adult  plumage. 

In  this  instance,  the  bright  feathers  of  the  wing  bow  were  relatively 
few  in  number,  while  the  hackle,  back,  and  saddle  feathers,  though  of 
adult  color  and  shape,  were  quite  short.  While  she  was  confined  during 
the  winter,  most  of  the  saddle  feathers  were  picked  off  by  her  mates. 
The  new  feathers  that  came  in  were  short,  rounded  at  the  end,  and  with- 
out barbuleless  barbs ;  the  ground  color  was  black,  the  distal  portion  of 
the  shaft  often  red,  and  the  web  sometimes  sprinkled  with  minute  brown 
spots.  As  somewhat  similar  feathers  may  often  be  seen  in  young  males, 
little  attention  was  paid  to  the  matter  until  late  in  the  summer  of  1914, 
when  it  was  observed  that  the  bird  was  not  developing  the  expected 
adult  male  coat  of  feathers.  The  shape  and  size  of  the  feathers  of  the 
new  coat  are  more  like  those  of  a  hen-feathered  male,  while  the  color 
of  the  feathers  of  the  back,  saddle,  and  wing  bow  remained  essentially 
as  described.  The  rest  of  the  bird  is  colored  like  a  male.  This  bird 
has  a  well-developed  comb,  wattles,  and  spurs,  and  in  a  sense  corre- 
sponds to  the  Type  II  of  the  ducks.  By  means  of  an  operation  it  has 
been  determined  that  no  ovary  was  present. 

FEMALE  FOWL  PARTIALLY  OVARIOTOMIZED. 

In  several  instances  the  ovary  has  not  been  entirely  removed ;  indeed, 
in  some  instances,  only  a  small  fraction  was  taken  out.  In  such  cases 
no  changes  followed  the  operation.  From  other  individuals  almost 
all  the  ovary  was  removed,  so  much  so  that  male  plumage  was  devel- 
oped in  varying  degrees,  though  no  definite  relation  between  the  amount 
of  ovary  removed  and  the  degree  to  which  the  secondary  sexual  char- 
acters of  the  male  developed  has  been  made  out,  because  the  exact 
amount  of  ovary  left  has  not  been  known,  though  in  a  few  instances 
none  could  be  seen  with  the  naked  eye. 

An  interesting  example  of  incomplete  removal  is  afforded  by  No. 
4140.  This  individual  was  a  hybrid  female,  whose  original  band  had 
become  lost.  She  was  about  3  months  old  at  time  of  operation  and 
had  well-developed  female  plumage.  The  removal,  according  to  the 
protocol,  was  probably  complete,  though  it  was  possible  that  a  little 


26  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

remained,  since  the  posterior  portion  did  not  come  off  as  neatly  as 
could  be  desired.  A  slow  hemorrhage,  however,  permitted  a  rather 
careful  examination  of  the  site  of  the  ovary,  and  this  showed  no  trace 
of  ovary.  September  22,  male  feathers  had  begun  to  appear,  but  after 
a  time  female  characters  appeared  on  the  younger  portions  of  the 
feathers  and,  of  course,  those  feathers  that  developed  after  this  were 
altogether  female.  December  14  an  examination  was  made.  At  the 
extreme  anterior  end  of  the  original  site  of  the  ovary  was  a  piece  the 
size  of  a  pin-head  with  a  few  ova  just  visible  to  the  naked  eye.  These 
ova  were  destroyed.  Near  the  center  of  the  site  were  3  ova,  each  3  or 
4  mm.  in  diameter,  which  were  left  in  place.  Careful  scrutiny  failed 
to  show  others.  No  ovary  was  visible  on  the  right  side  of  the  bird. 
August  1,  1913,  after  an  illness  of  several  weeks,  she  died  in  an  ema- 
ciated condition.  The  right  side  was  completely  empty.  On  the  left, 
in  the  same  situation  as  the  3  ova  mentioned  above,  which  had  in  the 
meantime  disappeared,  was  a  little  tissue  that  gave  no  indication  of 
being  ovarian.  The  oviduct  was  infantile.  At  death  the  plumage 
was  a  mixture  of  male  and  female  feathers,  but  the  numerous  new 
feathers  that  were  coming  in  were  all  male.  In  this  individual  there 
was  first  a  partial  assumption  of  male  characters,  followed  by  a  change 
to  female  characters  and  finally  again  to  male  characters.  These 
changes  paralleled  the  removal  of  all  but  a  minute  portion  of  the  ovary 
followed  by  a  partial  regeneration,  which  in  turn  was  either  removed 
or  degenerated. 

Other  instances  with  a  similar  history  might  be  described.  In  some 
only  a  few  feathers  developed  male  characters  partially  or  wholly  (plate 
VH,  fig.  F) ;  others  developed  more.  In  two  instances,  which  were  pure- 
bred Leghorns  of  the  same  stock  as  No.  2058,  each  developed  a  com- 
plete juvenile  male  plumage  by  early  fall.  Both  lost  the  feathers  from 
the  back  by  the  feather-eating  habits  of  their  companions,  and  in  each 
instance  the  new  feathers  that  came  in  were  female  in  character.  In 
June,  both  birds  were  opened  and  in  each  considerable  ovarian  tissue 
was  found  and  as  much  of  this  as  possible  was  removed.  Three 
weeks  later,  the  appearance  of  male  feathers  had  begun  in  both  birds, 
but  stopped  soon  after.  Later,  one  of  the  two  resumed  the  develop- 
ment of  male  characters.  In  several  others  the  spurs  continued  to 
develop,  although  the  plumage  reverted.  The  relation  of  spurs  to 
the  ovary  will  be  discussed  later  (page  38) . 

MALE  FOWL  PARTIALLY  OR  COMPLETELY  ORCHIDOTOMIZED. 

The  removal  of  the  testes  has  been  a  common  practice,  commer- 
cially, for  centuries,  in  order  to  increase  the  size  of  the  bird  and  also 
to  improve  its  flavor.  It  seems  probable,  however,  that  what  really 
happens  is  that  while  the  size  is  increased,  the  flesh  is  not  improved, 
but  remains  in  the  condition  of  the  young  bird  much  longer  than  it 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  27 

would  otherwise.  Whatever  improvement,  if  any,  in  flavor  is  due 
more  to  special  methods  of  fattening  than  to  removal  of  the  germ  glands. 
In  the  absence  of  the  latter,  the  capon  retains  certain  of  his  youthful 
characters  much  longer  than  he  would  otherwise,  but  it  is  very  doubt- 
ful whether  a  young  cockerel  fed  and  cooked  the  same  as  a  capon 
could  be  distinguished  by  taste  alone  from  the  latter.  Coinciding  with 
the  time  of  sexual  maturity,  the  cockerel  of  the  market  breeds  become 
"staggy,"  a  condition  characterized  by  a  hardening  of  the  muscles  with 
the  development  of  a  greater  amount  of  connective  tissue.  The  com- 
mercial advantages  of  caponizing  are  found  in  greater  size  and  slow 
maturity,  with  accompanying  retention  of  the  soft,  richly  flavored  flesh. 
Eventually,  however,  capons  become  hard  in  flesh. 

The  capon  has  been  investigated,  as  a  matter  of  scientific  interest, 
by  several  students — Foges,  Halban,  and  others.  They  reach  essen- 
tially the  same  results,  though  there  are  some  contradictions  which, 
however,  are  easily  explained.  They  are  agreed  that  while  the  comb 
and  wattles  remain  small,  the  plumage  is  essentially  like  that  of  the 
male,  except  that  it  lacks  brilliancy.  However,  normal  males  often  lack 
a  good  color,  due  to  late  hatching,  overcrowding,  poor  growth,  and 
other  unfavorable  conditions.  Indeed,  the  plumage  of  capons  when 
properly  cared  for  is  fully  as  brilliant  as  that  of  normal  males.  None 
of  these  observers  states  the  variety  of  fowls  used,  an  important  feature, 
as  the  males  of  some  breeds  have  very  small  combs  and  wattles.  The 
spurs,  too,  vary  much  in  the  age  at  which  they  appear.  In  Leghorns 
spurs  10  mm.  long  have  been  recorded  at  3  months  of  age.  In  some 
Plymouth  Rocks  and  Brahmas  they  are  just  beginning  to  appear  when 
the  birds  are  a  year  old.  If  this  variability  among  normal  males  be 
given  due  consideration,  the  discrepancies  in  the  observations  may  be 
accounted  for. 

For  the  present  study,  the  Leghorns  were  selected,  among  other 
reasons,  because,  first,  they  are  not  commonly  caponized ;  second,  in  each 
sex  the  comb  and  wattles  are  very  large;  third,  the  spurs  appear  in  the 
males  at  a  comparatively  early  age.  In  a  breed  with  these  character- 
istics we  find  the  following  histories  after  castration : 

Seven  pure-bred  Brown  Leghorns  were  castrated  when  from  21  to  28 
days  of  age,  although  commercially  males  are  caponized  at  2  to  3  months 
of  age.  At  this  time  they  possessed,  in  addition  to  the  down,  only 
remiges  and  rectrices.  Two  of  the  birds  were  kept  until  they  were  16 
months  of  age,  while  the  other  two  were  kept  until  4J  years  of  age. 
One  of  the  two  that  was  killed  at  16  months  had  long  been  recognized 
as  different  from  the  others.  He  was  more  active  and  inclined  to  pay 
attention  to  the  hens  and  grew  a  relatively  large  comb  and  wattles 
by  the  time  he  was  6  months  of  age.  However,  he  was  never  observed 
to  crow,  though  often  watched  and  though  particular  efforts  were  made 
to  get  him  to  crow.  On  making  the  autopsy,  a  piece  of  testicle  con- 


28  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

taining  spermatozoa  was  found  attached  to  the  abdominal  wall.  The 
sites  of  the  testes  were  empty.  The  other  bird,  externally,  was  char- 
acteristically a  capon  and  did  not  differ  from  his  mates.  At  death  no 
trace  of  testicular  material  could  be  found.  In  all  four  the  normal  male 
plumage  had  developed,  except  that  the  feathers  were  longer.  The 
spurs,  too,  were  well  developed.  The  comb  and  wattles,  however, 
remained  small,  though  of  course  not  of  the  size  they  were  when  the 
operation  was  performed.  The  two  kept  for  over  4  years  have  interest- 
ing histories.  When  18  months  old  their  combs  began  to  grow  rather 
rapidly  and  continued  to  grow  for  several  months  before  ceasing. 
During  the  winter  of  1913-14  the  combs  began  to  grow  again,  but, 
unfortunately,  during  the  severe  weather  lost  the  points  through  freez- 
ing. On  this  account  the  final  size  can  not  be  accurately  determined, 
but  it  is  obvious  that  they  reached  nearly  if  not  quite  their  normal  size. 

Further  experience  with  capons  shows  that  the  comb  development  of 
the  bird  figured  by  Goodale  (1913,  American  Naturalist)  is  greater  than 
that  which  occurs  in  other  instances,  such  as  that  shown  in  plate  vn,  A, 
which  has  almost  no  comb  development.  True,  the  comb  is  not  as 
small  as  when  the  bird  was  castrated,  but  the  enlargement  is  only  that 
necessary  to  correspond  to  the  increased  head  size.  It  is  now  evident 
that  the  comb  of  the  bird  figured  in  the  Naturalist  paper  had  already 
begun  to  grow  at  that  time,  although  for  a  bird  16  months  of  age  the 
comb  shown  in  the  figure  is  much  smaller  than  that  of  the  normal  hen, 
to  say  nothing  of  the  cock.  At  that  time  it  was  supposed  that  the 
amount  of  comb  tissue  present  was  due  to  the  genetic  basis  in  the  Leg- 
horns for  a  large  comb.  This  assumption  is  supported  by  the  absence 
of  testicular  tissue  in  a  mate  with  a  similar  history  which  was  autopsied 
and  by  the  relatively  rapid  growth  of  the  head  furnishings  in  another 
mate,  which  at  autopsy  had  a  small  bit  of  testicle  containing  sperma- 
tozoa, attached  to  the  abdominal  wall,  although  it  lacked  other  tes- 
ticular material.  The  capon  figured  in  the  Naturalist  was  killed  October 
17, 1915,  when  somewhat  more  than  4f  years  of  age.  The  bird  weighed 
5J  pounds  and  was  very  fat,  resembling  in  that  respect  an  old  hen  of  the 
American  breeds.  On  either  side  was  a  mass  of  testicular-like  material ; 
that  on  the  right  was  18  mm.  long  by  10  mm.  in  diameter,  that  on  the 
left  12  mm.  by  6  mm.  Leading  from  each  was  a  small  but  distinct 
vas  deferens.  No  spermatozoa  could  be  identified,  either  in  the  vas 
deferens  or  in  the  organ  itself.  Nor  was  there  any  evidence  of  sperm 
formation.  The  bird  was  in  good  health  and  had  been  running  with 
hens  for  a  long  time.  As  far  as  could  be  made  out,  the  " organs"  were 
in  good  condition. 

Although  both  birds  had  combs  of  similar  size  at  the  time  the  photo- 
graph mentioned  above  was  made,  eventually  one  (No.  1177)  out- 
stripped the  other,  developing  a  comb  that  was  only  a  little  smaller  than 
that  of  a  normal  male.  At  the  autopsy  of  No.  1177,  which  died  on 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  29 

July  16,  1915,  in  addition  to  organs  similar  to  those  of  No.  1192,  a 
piece  of  tissue,  3  by  5  mm.,  was  found  attached  to  the  mesentery,  which 
on  sectioning  proved  to  contain  no  spermatozoa  or  seminal  tubules. 
On  the  contrary,  its  structure  was  very  similar  to  that  of  the  same 
material  found  in  No.  1192.  The  possibility  that  this  tissue  is  really 
spermatogenic,  but  degenerate  because  of  its  age  and  its  position  on  the 
mesentery,  can  not  at  present  be  excluded,  owing  to  the  lack  of  suffi- 
cient comparative  material,  particularly  testes  from  normal  old  cocks. 
Testes,  however,  from  one  old  drake  and  one  old  cock  have  been 
examined  and  found  to  be  normal.  The  early  history  of  No.  1177 
is  similar  to  that  of  No.  1192,  but  his  later  history  differs  slightly  in 
that  his  head  furnishings  grew  to  a  larger  size  than  those  of  No.  1192. 
He  also  became  more  active  and  had  much  the  bearing  of  the  nor- 
mal cock. 

In  early  maturity  these  two  capons  were  not  kept  with  hens,  but 
with  cockerels.  During  the  winter  of  1912-13  they  ran  with  hens  along 
with  normal  males.  In  March  the  normal  males  were  removed ;  shortly 
after,  the  capons  were  observed  treading  the  hens.  They  were  never 
seen  chasing  the  hens,  but  when  hens  squatted  on  their  approach 
the  capons  mounted  them  and  completed  the  sexual  reaction.  There 
was  no  evidence  of  desire  on  the  part  of  the  capon,  but  his  reactions  to 
the  sight  of  the  receptive  hen  indicate  the  existence  of  an  instinctive 
complex  motor  response  to  the  specific  visual  stimulus. 

The  mating  reaction  between  normals  strengthens  the  interpretation 
given  of  the  capon's  behavior..  The  psychological  condition  of  each 
of  the  principal  actors  is  an  important  factor  in  determining  the  course 
of  the  mating  process.  As  a  rule,  the  male  is  always  ready  to  copulate. 
The  hens,  however,  vary.  Some  seem  always  ready,  others  never 
ready,  while  others  vary  from  time  to  time.  If  a  hen  is  ready  for  copu- 
lation she  will  squat  and  hold  out  her  wings  ready  for  the  male  to  mount 
whenever  he  approaches.  Under  such  circumstances  he  will  mount 
the  hen  and  complete  the  sexual  act,  even  though  as  far  as  one  can  see 
such  intention  was  far  from  his  mind.  In  other  words,  the  action  of 
the  hen  starts  a  complex  reflex.  Such  is  what  happens  when  a  mating 
occurs  between  the  capon  and  hen;  but  in  matings  between  normals 
it  often  happens  that  the  hen  is  not  ready  when  the  male  approaches, 
and  if  he  attempts  service  she  avoids  him.  If  he  is  particularly 
anxious  for  service  he  may  chase  her  and  eventually  force  service.  This 
sort  of  mating  has  not  been  observed  on  the  part  of  the  capons.  Their 
matings,  on  the  other  hand,  so  far  as  observed,  have  always  been  in 
response  to  the  female's  solicitation. 

For  surety's  sake,  a  large  number  of  the  eggs  of  these  hens  were 
examined,  but  all  were  found  to  be  infertile.  Later  in  the  season,  on 
two  or  three  occasions,  the  capons  were  seen  crowing.  The  crow 
was  to  all  intents  exactly  the  crow  of  a  normal  cock.  This  is  inter- 


30  GONADECTOMY   IN   RELATION  TO   THE    SECONDARY 

esting,  as  it  is  unlikely  that  the  birds  had  ever  crowed  before.  The 
reaction  was  shown  for  only  a  brief  period,  under  very  favorable 
weather  conditions  in  the  spring.  The  males  were  kept  with  the  females 
throughout  the  summer,  but  were  not  heard  to  crow  again  that  season, 
although  under  daily  observation.  The  mating  reflex,  however,  was 
also  kept  up. 

During  the  summers  of  1914  and  1915  these  capons  were  again 
allowed  to  run  with  a  large  flock  of  females  with  which  no  other  males 
were  kept.  The  behavior  of  these  birds  has  been  very  much  like  that 
of  a  normal  male.  I  have  not  seen  them  chase  the  hens,  but  have  seen 
them  tread  the  hens  under  the  same  circumstances  as  before.  Both 
crew  occasionally  and  No.  1177  crew  a  good  deal.  He  had  a  larger 
comb  than  the  other,  was  more  active,  and  carried  himself  in  the  erect, 
tense  posture  of  active  males  and  seemed  more  willing  to  tread  the  hens. 
The  pugnacity  of  both  was  tested  by  introducing  a  strange  male  from 
time  to  time.  On  one  or  two  occasions  a  fight  resulted,  in  one  of  which 
the  more  active  capon  (No.  1177)  came  off  victorious  for  the  time  being. 
After  a  few  hours,  however,  the  normal  male  returned  to  the  attack  and 
drove  both  the  capons  off  the  floor.  It  is  possible  that  the  temporary 
victory  of  the  capon  was  due  to  the  somewhat  dazed  condition  of  the 
male  when  placed  in  the  pen.  As  a  rule,  these  capons  have  either  left 
the  field  at  the  first  onslaught  or  fought  very  briefly.  Usually,  they  did 
not  make  the  first  attack. 

The  autopsies  on  these  birds  show  that  while  they  were  undoubtedly 
almost  completely  caponized,  there  was  a  regeneration  of  tissue,  the 
exact  nature  of  which  will  be  reported  upon  later.  It  seems  evident, 
however,  that  this  regeneration  must  have  been  slow  and  that  to  it 
must  be  referred  the  growth  of  comb  and  wattles  after  a  year  and  a  half. 

Of  another  set  of  4  Brown  Leghorns  castrated  August  5,  1913, 
3  proved  to  be  good  capons.  They  were  kept  with  hens,  males,  and 
other  capons  during  most  of  the  year.  Two  were  used  to  brood  chicks 
in  1914.  One  of  these  was  seen  crowing  in  September  of  that  year. 
He  was  also  noticed  circling  the  hens,  but  as  far  as  observed  did  not 
tread  any. 

A  number  of  Rhode  Island  Red  and  Silver  Penciled  Wyandotte 
capons  also  were  under  observation,  and  these,  too,  were  essentially 
similar  both  in  respect  to  appearance  and  behavior.  Several  of  these 
were  examined  and  found  to  be  completely  caponized;  in  others, 
however,  small  amounts  of  tissue,  like  that  noted  above,  were  found. 

The  results  of  removal  of  the  testes  from  the  young  cockerel  may  be 
stated  as  follows:  His  plumage  at  a  suitable  age  becomes  identical 
with  that  of  the  cock,  except  that  his  feathers  are  longer.  The  comb 
and  wattles  do  not  develop,  except  in  proportion  to  the  increase  in 
skull  size.  The  spurs  are  like  those  of  the  cock,  but  become  pointed 
at  an  age  when  the  latter's  are  still  blunt.  His  behavior  is  anomalous  in 


SEXUAL   CHARACTERS   OP   SOME   DOMESTIC   BIRDS.  31 

that,  though  usually  quiet  and  voiceless,  he  sometimes  crows,  sometimes 
shows  the  male  sexual  reaction,  and  may  brood  chicks.  (Plate  VH,  fig.  G.) 
There  is  another  peculiarity  of  the  capon  that  I  have  never  seen 
described,  although  it  seems  impossible  that  it  could  have  escaped 
notice.  The  first  row  of  coverts  covering  the  primaries  become  dispro- 
portionately long,  while  the  secondary  coverts  retain  their  normal  pro- 
portions. The  disproportion  is  shown  in  plate  VH,  E.  This  increased 
size  of  the  primary  coverts  is  of  considerable  importance,  since  it  indi- 
cates that  the  feathers  differ  in  their  response  to  the  secretions  of  the 
testes.  While,  as  stated  above,  the  feathers  of  the  capon  in  general 
are  longer  than  those  of  the  cock,  the  coverts  grow  much  longer  than 
any  of  the  neighboring  feathers. 

AGE  IN  RELATION  TO  GONADECTOMY. 

The  age  at  which  the  operation  is  performed  may  influence  the  final 
results  in  one  of  two  ways:  First,  the  character,  such  as  a  mature 
feather,  may  have  ceased  growing  and  therefore  be  non-modifiable. 
Secondly,  it  may  be  still  growing,  or  it  may  resume  its  growth  sub- 
sequent to  the  operation,  so  that  in  either  case  there  is  the  possi- 
bility of  modification.  Moreover,  age  might  influence  the  type  of 
modification  through  its  action  on  other  parts  of  the  body.  That  is, 
a  bird  castrated  when  3  weeks  old  might  give  an  entirely  different 
result  from  one  castrated  at  3  months,  but  thus  far,  aside  from  structures 
which  are  no  longer  growing  and  therefore  no  longer  subject  to  the 
influence  of  the  gonad,  no  constant  relation  to  age  has  been  observed. 

Since,  however,  the  young  bird  is  less  differentiated  than  the  older, 
greater  changes  would  be  expected.  If  it  were  possible  to  destroy  the 
germ  glands  at  the  proper  time  during  the  embryonic  life,  the  female 
embryo  possibly  might  become  transformed  somatically  into  a  male. 

AGE  OF  THE  FEATHER  GERM  IN  RELATION  TO  THE  TYPE  OF 
FEATHER  DEVELOPED. 

It  has  happened  in  a  number  of  instances  that  the  female  bird  has 
been  molting  at  the  time  of  the  operation.  Individual  feathers  from 
such  birds  often  show  both  male  and  female  colors,  color  patterns,  and 
even  shapes,  the  area  occupied  by  each  depending  upon  the  age  of  the 
feather  germs;  the  younger  the  feather  the  larger  the  area  of  male 
characters.  The  colors  are  often  separated  by  a  clear-cut  transverse 
line  in  both  ducks  and  chickens.  The  effect  is  more  striking  in  feathers 
from  fowls  than  in  those  from  ducks,  largely  because  of  the  kind  of 
characters  involved.  The  cleanest-cut  instances  have  been  observed  in 
Brown  Leghorn  pullets,  particularly  in  the  breast  feathers,  which  are 
salmon-colored  in  the  normal  female  but  black  in  the  male.  The 
modified  feathers  are  salmon-colored  at  the  distal  end,  but  at  some 


32  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

more  proximal  point  change  abruptly  to  black.  The  position  of  the 
line  separating  the  two  colors  varies  with  the  age  of  the  feather  germ 
at  the  time  of  the  operation,  those  feathers  which  have  the  greatest 
amount  of  black  (i.e.,  which  have  the  line  nearer  the  tip)  having  been 
the  youngest  when  the  ovary  was  removed.  The  line  of  demarcation 
is  sharp,  showing  that  the  secretion  of  ovary  does  not  persist  in  the 
circulation  for  any  considerable  length  of  time  after  the  ovary  has  been 
removed.  A  series  of  such  feathers  is  shown  in  plate  vi,  a  to  g. 

Many  of  the  combinations  theoretically  possible  have  been  observed. 
The  distal  end  of  the  sickles  may  be  stippled  brown  and  black  (female) , 
the  proximal  end  a  uniform  glossy  black  (male),  or  vice  versa,  the 
latter  occurring  where  the  ovary  regenerated.  Saddle  feathers  may  be 
observed  with  male  tips  and  female  bases  (plate  vi,  i) ;  others  may  have 
partially  female  tips  and  male  bases  (plate  vi,  s) ;  while  a  third  group 
has  been  seen  with  female  tips,  male  intermediate  portions,  and  female 
bases  (plate  vi,  h) .  In  these  instances,  while  the  male  end,  for  example, 
is  colored  like  that  of  the  female,  its  shape  may  be  more  like  that  of  the 
female,  or  vice  versa.  Indeed,  some  of  the  expected  combinations, 
while  realized  in  point  of  color,  are  not  realized  in  point  of  shape,  size, 
and  arrangement  of  barbules.  Thus  the  tip,  while  rounded,  may  be 
narrower  than  in  the  case  of  purely  female  feathers.  This  lack  of 
expected  combinations  may  be  due  to  the  amount  of  differentiation 
already  undergone  by  the  cells  of  the  feather  germ  at  the  time  of  the 
operation.  That  is,  the  cells  for  the  feathers  may  already  be  cut  off, 
but  there  are  not  enough  to  produce  a  full-sized  male  feather.  Or, 
the  large  outlines  of  the  feather  may  be  already  laid  down,  and  hence 
unchangeable,  while  the  color  has  not  yet  been  determined.  The 
observed  combinations  are  undoubtedly  due  to  the  mechanical  and 
time  relations  in  the  development  of  the  various  parts  of  the  feather. 
Thus,  it  is  not  very  likely  that  any  feather  will  have  a  very  broad, 
rounded,  and  stippled  tip,  followed  by  a  narrow  black  portion  with 
golden  margin,  as  such  feathers  are  too  short  to  permit  a  change  of 
this  character.  That  is,  it  is  probable  that  if  the  distal  end  of  the 
feather  has  been  laid  down  so  as  to  produce  a  typical  female  feather,  a 
considerable  change  in  the  basal  end  will  have  been  rendered  impossible. 

When  the  removal  of  the  ovary  has  been  so  incomplete  that  male 
characters  develop  in  the  plumage  for  a  time  only  and  then  cease, 
feathers  male  at  the  distal  end  but  female  at  the  proximal  end  may  be 
observed.  For  example,  instead  of  a  buff  tip  and  slate  base,  which  is 
normal  for  female  feathers,  there  may  be  a  black  tip  followed  by  only 
the  slate-colored  base.  Since  the  under-color  (proximal  half)  of  the 
normal  female  breast  feathers  is  slate  and  merges  gradually  with  the 
salmon  tip,  the  line  of  separation  is  not  as  clear  as  in  the  reverse  case. 
Similarly,  the  tip  of  the  saddle  feathers  may  be  male,  the  base  female 
(plate  vi,  i).  In  one  case,  the  tip  of  the  saddle  feathers  were  female  for 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  33 

several  millimeters,  together  with  the  center  and  most  of  the  base,  but 
along  the  edges  of  the  tip,  for  about  6  mm.,  the  feathers  were  dis- 
tinctly male,  the  barbules  being  absent  and  the  barbs  orange  in  color. 

Like  results  have  been  obtained  in  several  instances  with  the  ducks, 
but  in  only  one  is  the  interpretation  free  from  complications,  due  to 
the  close  resemblance  of  the  female's  plumage  with  both  the  juvenile 
and  summer  plumages  of  the  male  and  partly  to  the  type  of  plumage 
found  in  the  females  of  Type  II.  There  is  no  question,  of  course,  as  to 
the  nature  of  the  male  portion  of  the  feather,  provided  it  belongs  to  the 
breeding  plumage.  Whatever  questions  may  arise  are  in  regard  to  the 
female  portion.  Plate  vi,  p,  shows  one  of  these  feathers.  Doubtless 
more  instances  would  have  come  under  observation  if  particular  pains 
had  been  taken  to  select  birds  in  the  right  stage  of  development  when 
operated  on. 

Feathers  that  even  for  a  small  portion  are  male  along  the  margin  but 
female  in  the  center,  or  vice  versa,  do  not  fit  well  with  the  suggestion 
that  the  ovarian  secretion  does  not  persist  long  hi  the  circulation. 
However,  another  sort  of  explanation  may  perhaps  be  offered  for  such 
cases,  and  that  is  that  some  of  these  characters  are  more  responsive  to 
slight  amounts  of  the  ovarian  secretion  than  others.  From  the  evi- 
dence presented  above,  it  is  quite  certain  that,  although  a  minute 
particle  of  the  ovary  may  be  present,  the  amount  of  secretion  produced 
may  be  insufficient  to  bring  about  the  development  of  the  female 
characters.  As  this  particle  grows  the  amount  of  secretion  produced 
must  constantly  increase  until  it  reaches  a  point  where  the  male  char- 
acters are  completely  suppressed.  In  between  these  may  be  a  region 
where  the  amount  of  secretion  present  in  the  blood  is  sufficient  to 
suppress  some  male  characters,  but  not  all. 

A  different  explanation  may  be  offered  to  account  for  those  instances 
where  the  color  distribution  in  a  transverse  line  is  both  male  and  female, 
but  where  this  condition  covers  a  very  small  portion  of  the  feather  and 
then  gives  way  to  a  purely  male  or  female  condition,  as  the  case  may  be, 
since  obviously  the  relation  of  the  barbs  to  the  axis  while  in  the  sheath 
is  sufficient  to  account  for  the  final  relationship  of  the  characters. 

The  whole  matter  is  further  complicated  by  considerable  variation 
in  the  characters  in  question,  in  some  portions  of  the  plumage  at  least. 

It  may  be  possible  to  utilize  this  sort  of  data  in  studying  the  order 
in  which  the  various  parts  of  the  feather  are  laid  down.  Thus,  those 
feathers  that  have  the  margin  on  any  transverse  line  of  one  color  and 
the  center  of  another  color  indicate  that  the  corresponding  parts  in  the 
feather  germ  are  differentiated  at  different  times,  the  margin  being 
formed  later  than  the  center.  On  the  other  hand,  from  those  feathers 
in  which  the  transverse  boundary  line  between  the  two  colors  is  very 
sharp,  one  could  conclude  that  the  differentiation  extends  in  a  well- 
defined  line  transversely  to  the  main  axis  of  the  feather  cylinder. 


34 


GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 


TWO  TYPES  OF  FEMALES  RESULTING  FROM  OVARIOTOMY. 

In  the  course  of  the  work  it  has  been  necessary  to  use  both  pure-bred 
and  cross-bred  female  birds.  Curiously,  in  the  case  of  the  ducks,  the 
cross-breds  after  the  operation  have  developed  a  more  perfect  resem- 
blance to  the  male's  plumage  than  the  pure-bred.  Not  one  of  the  lat- 
ter (five  in  number)1  has  produced  a  bird  that  did  more  than  develop 
male  plumage  to  a  certain  degree,  while  the  plumage  of  the  least  perfect 
of  the  cross-breds  approximates  that  of  the  male  more  closely  than  the 
most  perfect  of  the  pure-breds.  The  results  with  the  pure-breds  are 
not  due  to  imperfect  castration,  for  this  type  of  plumage  is  maintained 
for  years,  in  one  instance  for  nearly  6  years.  Moreover,  at  autopsy  the 
birds  have  been  found  free  of  any  ovarian  tissue.  During  the  second 
winter  the  plumage  is  frequently  more  male-like  than  during  the  first 
winter.  Two  of  the  pullets  also  failed  to  develop  a  perfect  coat  of  male 
feathers,  though  they  were  the  ones  that  developed  the  comb  and  wattles 

TABLE  4. — Comparison  of  the  two  types  of  female  ducks  resulting  from  ovariotomy. 


Type  I. 

Type  II. 

Head 

Drake 

Some  green  feathers,  especially  dorsally. 

Re- 

Neck  ring 

Present 

mainder  female-like. 
Present. 

Breast 

Drake 

Mixed  brown  and  buffs,  but  not  arranged  in 

the 

Belly  

Drake           

female  pattern.      Feathers  of   this  type 
shown  in  plate  vi  figs,  r  and  q. 
Mixed  drake  and  duck. 

are 

Shoulders  

Drake  

Mixed  drake  and  duck. 

Back  

Drake  

Drake. 

Wings  

Drake  

Drake. 

Rump  

Drake  

Drake. 

Tail  feathers  .... 

Curled  

Curled. 

Bill  
Voice  

Black  and  yellow  .... 
Duck  

Black  and  yellow. 
Duck. 

which  most  perfectly  resembled  those  of  the  male.  They  also  were  pure- 
bred. Many  of  the  cross-bred  ducks,  however,  failed  to  develop  into  quite 
as  good  replicas  of  the  male  as  No.  169.  A  few  feathers  in  certain  parts 
of  the  body  retain  a  resemblance  to  the  female,  so  that  on  the  whole  the 
demarcation  between  the  two  groups  is  not  altogether  clear-cut,  though 
there  is  little  difficulty  in  placing  an  individual  in  the  proper  class. 
The  difference  between  the  two  types  is  shown  in  table  4.  The  word 
" drake"  or  "duck"  is  used  to  indicate  that  the  character  in  question 
is  like  that  of  the  male  or  female  respectively. 

If  we  survey  the  cases  in  which  the  male  plumage  is  the  more  imper- 
fectly developed,  it  appears  that  those  regions  which  in  the  males 
become  most  like  the  females  during  the  summer  molt  are  the  same 
regions  that,  in  the  castrated  females,  tend  most  strongly  to  retain  female 
characters.  These  regions  are  the  head  and  ventral  surface,  especially 

xTwo  non-pedigreed  females,  probably  but  not  certainly  pure-bred,  castrated  in  1914,  belong 
to  this  class. 


SEXUAL   CHARACTERS   OF    SOME    DOMESTIC   BIRDS.  35 

the  breast  and  belly.  In  the  belly  region  the  markings  of  the  feathers 
in  both  the  castrated  female  and  the  male  in  summer  plumage  are 
vague,  but  usually  show  a  certain  amount  of  vermiculation.  The 
feathers  of  the  breast  regions  in  each  of  the  three  plumages  (breeding 
male,  summer  male,  and  female),  however,  have  a  distinct  pattern, 
which  is  often  very  varied  and  exceedingly  difficult  to  describe  briefly. 
In  the  female,  the  feathers  are  brown,  penciled  concentrically  with  buff 
or  else  more  or  less  spotted  (cf.  plate  vi,  figs,  m  and  o).  In  the  male 
they  are  self-colored  claret.  In  the  summer  plumage  of  the  male  they 
are  again  distinct,  having  a  reddish  tip,  the  remainder  being  buff  and 
brown,  but  with  at  least  one  or  two  transverse  bars  (cf.  plate  vi,  figs,  r 
and  q).  In  the  castrated  female  the  feathers  of  this  region  approach 
most  closely  to  the  latter  type.  The  transverse  buff  or  reddish-buff  bars 
are  characteristic  of  the  summer  plumage  of  the  male  and  of  Type  II 
females.  Certainly  they  bear  no  resemblance  to  the  plumage  of  either 
the  breeding  male  or  female.  In  the  head  region  of  the  castrated 
females  a  mosaic  is  usually  formed,  part  of  the  feathers  being  distinctly 
male,  the  other  of  a  nondescript  semi-female  character.  The  remainder 
of  the  dorsal  region  is  always  approximately  male,  except  for  some  of 
the  scapulars. 

Why  so  many  of  the  castrated  females  should  develop  a  plumage 
that  in  part  is  very  much  like  the  summer  plumage  of  the  male  is  not 
at  all  clear.  It  can  not  be  due  to  the  absence  of  all  gonads,  as  recorded 
above,  for  in  the  male  the  absence  of  such  gonads  results  in  a  failure  of 
the  male  to  assume  the  summer  plumage.  Moreover,  this  plumage  is 
not  characteristic  of  all  castrated  females,  since  some  develop  the 
entire  male  breeding  plumage.  It  would  seem  more  likely  that  the 
plumage  of  Type  II  is  the  result  of  some  peculiarity  in  the  gametic  con- 
stitution of  the  bird. 

Possibly  an  explanation  of  this  peculiar  behavior  may  be  found  in 
the  following  suggestions :  In  poultry  breeding,  what  is  known  as  the 
double-mating  system  is  used  to  secure  individuals  which  come  nearest 
to  the  standard  requirements.  The  term  " double  mating"  means 
simply  that  two  separate  lines  are  used  to  secure  the  standard  male  and 
female  respectively.  The  female  from  the  standard  male  line  and  the 
male  from  the  standard  female  line  are  wasters.  In  the  last  analysis,  it 
means  that  to  get  a  pair  of  show-room  birds  the  females  are  bred  from 
one  strain,  the  males  from  another,  each  strain  being  carefully  bred  by 
itself.  In  Rouen  ducks  the  breeder  endeavors  to  produce  a  female  with 
clean-cut  concentric  penciling  of  the  type  shown  in  plate  vi,  o.  The 
male  of  the  female  line,  though  without  penciling  in  the  adult  plumage, 
often  has  well-developed  penciling  in  the  juvenile  or  summer  plumage, 
and,  other  things  being  equal,  those  males  having  the  best  penciling 
are  chosen  as  breeders  for  standard  females. 

Under  such  selection  it  follows  that  the  flock  as  a  whole  is  held  reason- 
ably close  to  one  end  of  the  curve  of  variation.  In  the  cross-breds  the 


36  GONADECTOMY   IN   KELATION   TO   THE   SECONDARY 

effects  of  this  variation  might  be  largely  or  completely  lost  and  the 
character  returned  to  the  normal  condition  for  the  species.  The 
feathers  of  the  cross-bred  female,  while  variable,  are  not  penciled  as 
a  rule,  but  are  splashed  in  various  ways  (plate  vi,  m).  In  the  pure- 
bred stock,  then,  the  constitution  of  the  bird  seems  to  be  less  variable, 
and  even  after  the  removal  of  the  ovary  tends  strongly  to  continue  its 
development  in  the  same  course  that  it  had  with  the  ovaries  present. 
In  other  words,  the  constitution  of  the  pure-bred  female  has  been 
modified  by  selection  in  a  given  direction,  so  that  it  is  in  a  measure 
independent  of  the  internal  secretion  produced  by  the  ovary.  In  the 
cross-bred,  on  the  other  hand,  this  modification  has  been  lost  for  the 
most  part  and  the  female  characters  are  dependent  on  the  secretion  of 
the  ovary.  Whether  or  not  the  explanation  has  any  real  basis  in  fact, 
it  is  evident  that  ovariotomy  by  itself  is  not  always  sufficient  to  trans- 
form a  female  into  the  replica  of  a  male. 

EFFECTS  OF  GONADECTOMY  ON  PARTICULAR  PARTS  OF  THE  BODY. 

EFFECT  ON  PLUMAGE. 

Of  the  various  parts  of  the  body  affected  by  gonadectomy  the  most 
striking  changes  perhaps  occur  in  the  plumage  of  the  female.  The 
plumage  of  the  male  is  altered  comparatively  little;  some  feathers 
grow  somewhat  longer,  but  otherwise  they  are  the  same  as  in  the  un- 
altered male.  In  contrast  the  plumage  changes  in  the  female  after 
ovariotomy  are  extensive,  both  in  respect  to  shape,  size,  color,  and 
color  pattern.  Short  feathers  become  long;  straight  feathers  curved; 
feathers  with  broad  rounded  ends  become  narrow  and  pointed.  A 
portion  of  the  barbs  become  converted  into  bristles.  The  color  changes 
are  so  numerous  that  only  a  few  of  them  need  be  noted.  Salmon 
feathers  become  black;  stippled  brown  feathers  become  golden  with  a 
black  central  stripe,  or  black  and  brown  penciled  become  gray  and  black 
vermiculated. 

It  is  noteworthy  that  of  all  these  changes  none  occurs  in  pairs, 
being  promiscuous;  this  indicates  that  only  two  possibilities  are  avail- 
able and  that  the  action  of  the  ovarian  hormone  determines  which  of 
the  two  possibilities  develops. 

EFFECT  ON  HEAD  FURNISHINGS. 

The  Brown  Leghorns  offer  especially  good  opportunities  for  deter- 
mining the  status  of  the  capon's  comb.  It  has  been  believed  that  his 
comb  is  that  of  the  hen,  and  this  is  cited  as  an  instance  of  the  assump- 
tion of  female  characters  by  the  castrated  male.  It  requires  only  a 
cursory  familiarity  with  the  different  races  of  fowl  to  observe  that  the 
size  of  the  comb  is  an  extremely  variable  character,  although  within 
certain  rather  large  limits  it  is  constant  for  each  race.  Thus,  in  certain 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  37 

strains  of  Plymouth  Rocks,  the  fully  developed  comb  of  the  male  is  very 
much  smaller  than  that  of  the  Brown  Leghorns,  though  the  latter  are 
only  half  the  weight  of  the  Plymouth  Rocks.  The  female  Minorca  has 
a  larger  comb  than  that  of  the  Plymouth  Rock  male,  but,  of  course,  the 
combs  of  the  Minorca  males  are  correspondingly  larger.  Moreover,  in 
most  instances  the  comb  of  the  male  has  a  proportionally  larger  blade 
than  that  of  the  female.  A  further  difference  is  found  in  the  texture  of 
the  comb,  that  of  the  female  being  finer  than  that  of  the  male.  Finally, 
in  the  female  Leghorn  and  similar  breeds  the  comb  almost  always  lops 
to  one  side.  This  secondary  sexual  character  is  not  universal  among 
domestic  fowl,  but  is  most  common  in  the  Mediterranean  races.  Or- 
dinarily, capons  are  derived  from  the  low-combed  races,  a  circumstance 
which  has  made  it  difficult  to  say  that  the  capon's  comb  is  not  feminine. 
In  the  Leghorns,  however,  the  capon's  comb  is  practically  undeveloped. 
Therefore,  the  only  possible  conclusion  is  that  the  capon's  comb  and 
wattles  are  infantile.  They  do  not,  of  course,  remain  of  the  same  size  as 
that  of  the  chick  at  the  time  of  the  operation.  The  base  of  the  comb 


Comparative  size  of  the  combs  of  Brown  Leghorn  fowls. 

a,  an  adult  male.     6  and  c,  two  adult  females,     d,  an  adult 
capon.     Drawing  one-half  natural  size. 

increases  in  length  with  the  increase  in  size  of  the  skull.  The  height 
of  the  comb  also  increases  somewhat  in  absolute  size,  but  not  in  pro- 
portion to  the  comb  length.  The  comb  of  the  Leghorn  capon,  however, 
is  about  the  same  size  as  that  of  some  Plymouth  Rock  females.  The 
comparative  sizes  of  the  combs  of  the  normal  Brown  Leghorn,  male  and 
female,  and  of  the  capon  are  shown  in  the  accompanying  text-figure. 

In  the  castrated  females,  the  comb  has  developed  in  varying  degrees, 
becoming  very  large  and  male-like  in  some,  while  hi  others  it  has 
remained  comparatively  small.  As  yet  there  is  no  clear  evidence  of 
the  causes  of  this  difference.  Certainly  it  is  not  connected  with  the 
hypertrophy  of  the  Wolffian  body,  for  this  has  been  found  in  every 
individual.  The  birds  with  large  combs,  as  a  rule,  have  been  younger 
when  castrated  than  those  with  small  combs,  but  general  conclusions 
can  not  be  drawn  from  the  few  instances  available. 


38  GONADECTOMY   IN   RELATION   TO   THE   SECONDARY 

EFFECT  ON  SPURS. 

There  are  contradictory  statements  in  the  literature  regarding  the 
effect  of  castration  on  the  spurs  of  the  male,  some  observers  having 
even  reported  an  absence  of  spurs  in  capons.  All  the  capons  reported 
in  this  paper  have  well-developed  spurs,  but  it  by  no  means  follows 
that  the  observations  to  the  contrary  were  incorrect,  as  in  some  nor- 
mal cocks  (Brahmas  and  similar  races  especially)  the  spurs  are  very  slow 
in  developing.  One  White  Plymouth  Rock  male  at  15  months  had  not 
developed  a  spur  on  one  shank,  while  the  spur  on  the  other  was  very 
small.  As  far  as  my  own  experiments  and  observations  go,  the  capon 
develops  essentially  the  same  amount  of  spur  tissue  as  the  cock.  The 
spurs  of  the  capon,  however,  develop  somewhat  differently.  They 
become  pointed  soon  after  their  eruption,  and  by  the  time  they  are 
half  an  inch  in  length  they  have  the  form  of  a  perfect  cone  instead  of 
the  truncate  cone  of  the  normal  male.  Later  they  become  indistin- 
guishable from  those  of  the  adult  male. 

The  normal  female  is  usually  without  spurs,  yet  hens  that  in  all 
other  respects  are  perfectly  normal,  as  far  as  outward  appearances  are 
concerned,  sometimes  develop  spurs.  In  such  instances  the  spurs 
may  be  of  equal  size  on  both  shanks,  symmetrical,  and  as  long  as  those 
of  the  male;  or  they  may  be  small,  irregular  in  shape,  and  equal  or 
unequal  in  size.  In  one  individual  observed,  the  left  spur  is  a  fine, 
long  specimen,  while  the  right  is  small  and  irregular  in  shape,  pro- 
jecting scarcely  more  than  5  mm.  from  the  shank.  Such  hens  are 
normal,  at  least  as  far  as  egg-production  is  concerned.  The  writer 
has  had  at  various  times  several  hens  with  well-developed  spurs  and 
has  reared  numerous  chicks  from  them  in  the  endeavor  to  produce  a 
race  of  birds  in  which  each  sex  might  be  spurred.  As  yet  this  result 
has  not  been  secured,  but  that  it  is  attainable  is  shown  by  the  fact 
that  some  strains  of  Leghorns  and  Minorcas  produce  a  large  percentage 
of  spurred  female  offspring.  In  one  instance  a  Leghorn  cock  crossed  on 
some  Plymouth  Rock  hens  gave  a  progeny  of  which  the  females  were 
spurred  in  varying  degrees.  Thus,  there  is  some  indication  that  the 
origin  of  normal  spurred  hens  is  to  be  found  in  their  genetic  constitutions. 
The  mere  presence  of  spurs,  then,  is  not  necessarily  to  be  taken  as  an 
indication  of  the  assumption  of  a  male  character  any  more  than  the 
presence  of  horns  in  the  female  reindeer  or  domestic  cattle  is  a  similar 
indication  of  an  abnormal  ovary.  If,  however,  the  functions  of  the 
ovary  as  an  organ  of  internal  secretion  is  suspended,  the  spurs  develop, 
and  this  development  may  continue  even  after  the  functions  have  been 
resumed.  Well-developed  spurs  have  been  observed  in  all  females 
castrated  in  which  the  male  plumage  also  developed,  while  in  many  of 
those  in  which  the  assumption  of  male  plumage  was  partial  or  tem- 
porary the  spurs  started  to  grow.  Several  times  they  continued  to 
grow  after  the  plumage  reverted,  and  though  they  did  not  grow  quite 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  39 

as  long  as  those  in  which  the  removal  of  the  ovary  was  complete,  they 
were  otherwise  similar.  The  spurs  became  attached  to  the  shank 
bone  and  had  the  same  symmetry  as  those  from  completely  castrated 
hens.  Apparently,  the  dependence  of  the  spurs  upon  the  internal 
secretion  is  relatively  slight,  or,  to  look  at  the  matter  the  other  way, 
the  inhibition  exerted  in  the  female  upon  the  development  of  the  spurs 
is  so  slight  that  once  development  starts  the  hormone  is  not  always 
able  to  check  it. 

EFFECTS  ON  THE  VOICE  AND  ASSOCIATED  ORGANS. 

Castrated  ducks  of  both  sexes,  with  the  exceptions  noted  above,  have 
undergone  no  change  in  voice.  Each  has  retained  the  voice  of  the 
normal  bird  and  each  exercises  its  voice  in  a  manner  and  to  a  degree  quite 
the  same  as  the  uncastrated  bird,  except  that  some  castrated  females 
occasionally  give  voice  to  a  sound  similar  to  the  drake's.  Nor  has  any 
change  been  observed  in  the  development  of  the  syrinx  in  either  sex. 

In  fowls  the  effects  are  more  marked.  Castrated  individuals  of  each 
sex  are  disinclined  to  give  voice  to  any  sort  of  sound.  Capons  are 
capable  of  giving  voice  to  all  the  sounds  of  which  the  cock  is  capable, 
but  rarely  do  so,  remaining  (so  far  as  ordinary  experience  goes)  voice- 
less for  long  periods  of  time.  Of  course,  it  may  happen  that  they  use 
their  voice  more  than  noticed,  but  certainly  to  no  such  degree  as  that  of 
the  cocks  nearby. 

The  castrated  females  have  been  equally  quiet.  I  have  never  heard 
one  crow  or  attempt  to  crow.  One  has  occasionally  been  heard  to  cluck, 
making  a  sound  that  resembled  the  calling  of  the  cock  to  the  hens  for  a 
tid-bit .  Another  was  induced  to  ' '  cr-r-r-r-k ' '  like  a  hen  on  one  occasion. 
Aside  from  these  instances,  and  a  squawk  when  handled  roughly,  they 
remain  voiceless. 

EFFECT  ON  THE  MOLT. 

As  far  as  my  observations  go,  castration  with  one  exception  has  not 
influenced  the  molt  of  the  capon.  A  definite  statement  in  regard  to  the 
molt  of  the  poullard  can  not  be  made  at  present.  In  some  instances  a 
molt  comparable  to  the  summer  molt  of  the  ducks  has  occurred,  with 
corresponding  changes  hi  plumage,  as  described  for  No.  4471.  A  com- 
parable change,  noted  for  No.  3840  and  No.  2058  in  1915,  has  been 
described  in  detail  elsewhere  (Goodale,  1916).  Other  individuals,  how- 
ever, may  not  pass  through  such  a  molt,  while  the  same  individual  may 
not  show  the  molt  each  year.  Thus  No.  4471  exhibited  the  molt  in  1914, 
but  not  in  1913  or  1915.  No.  4290,  though  of  the  same  age  as  No.  4471, 
did  not  pass  through  this  molt  in  either  of  her  two  adult  summers. 

The  castrated  ducks,  however,  have  behaved  very  differently.  They 
molt  several  times  each  year  and  often  without  any  definite  relation  to 
the  normal  molts  of  the  adult.  During  the  early  period  of  then*  life, 
while  they  are  growing  the  juvenile  and  adult  coats  of  feathers,  they 
molt  at  the  same  time  that  the  normal  birds  do.  The  normal  adult 


40  GONADECTOMY   IN   RELATION   TO   THE    SECONDARY 

Rouen  undergoes  the  following  molts:  Sometimes  in  early  summer, 
usually  in  June  and  July,  the  actual  date  varying  a  great  deal  with 
different  individuals,  each  sex  molts,  the  new  coat  of  the  male  forming 
the  so-called  summer  plumage,  while  that  of  the  female  is  not  very 
different  from  that  worn  during  the  breeding  plumage.  Early  in  the 
fall  each  sex  molts  again,  the  male  this  time  resuming  his  breeding 
plumage.  The  flights,  however,  are  only  molted  once.  Thus,  there 
is  an  interval  of  3  or  4  months  during  the  summer  when  each  sex  is  in 
a  state  of  almost  continuous  molt  in  some  part  or  other  of  the  body. 
For  the  other  8  or  9  months  the  birds  ordinarily  retain  the  coat  devel- 
oped in  the  fall,  i.  e.,  the  breeding  plumage.  But  the  castrated  indi- 
viduals of  each  sex  molt  at  irregular  intervals  throughout  the  year. 
The  molt  is  extensive  in  that  it  includes  nearly  all  the  feathers  except 
those  of  the  wing.  The  new  plumage  is  like  the  one  that  preceded  it, 
except  in  the  case  of  those  females  that  have  assumed  the  summer 
plumage  of  the  male. 

Castration  of  the  drake  has  a  remarkable  influence  on  the  summer 
molt.  During  the  same  period  of  the  year  that  the  normal  drake  is 
taking  on  the  summer  plumage,  the  castrated  individuals  molt,  but  do 
not  assume  the  summer  plumage.  Instead,  the  new  feathers  are  like 
the  old.  This  is  clear  evidence  that  the  testes  control  the  characters 
of  the  summer  coat.  This  coat  imitates  that  of  the  female,  but  does 
not  duplicate  it,  though  feathers  in  certain  regions  of  some  males  are 
indistinguishable  from  those  of  the  female.  Perhaps  an  explanation  of 
this  relation  can  be  found  in  the  following  considerations :  The  summer 
plumage  begins  to  develop  when  the  breeding-season  is  at  its  height — 
i.  e.,  at  the  time  of  the  greatest  sexual  activity — or  at  least  soon  after 
it  has  reached  its  climax,  usually  in  June  or  early  July.  During  this 
period  the  males  are  most  active  hi  treading  the  females  and  naturally 
the  testes  are  at  the  period  of  greatest  activity.  The  so-called  breed- 
ing plumage,  however,  develops  in  early  autumn,  after  the  breeding 
season  is  over,  when  the  males  are  least  active  and  when  the  testes  are 
in  a  state  of  comparative  repose.  The  changes  may  or  may  not  be 
connected  with  the  greater  production  of  spermatozoa  at  this  season  of 
the  year,  but  may  be  dependent  on  some  other  physiological  change  in 
the  testes.  An  attempt  will  be  made  to  test  this  hypothesis  by  pulling 
feathers  during  the  breeding  season,  some  months  ahead  of  the  normal 
molt,  on  the  assumption  that  the  state  of  eclipse  is  due  to  changes  in  the 
testes  resulting  from  their  activity.1 

Although  it  is  perfectly  clear  that  following  castration  the  drake 
may  not  assume  the  summer  plumage,  it  is  not  yet  certain  that  com- 
plete castration  in  the  sense  of  removal  of  both  the  spermatogenic  por- 
tion and  efferent  ducts  (epididymis)  is  necessary  for  this  result. 

xThe  experiment  was  tried  in  the  spring  of  1916,  with  results  agreeing  with  the  hypothesis 
proposed. 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  41 

EFFECT  ON  COLOR  OF  THE  MANDIBLE. 

The  effect  of  castration  on  the  color  of  the  upper  mandible  does  not 
correspond  to  that  observed  for  plumage-color.  No  change  has  been 
noted  in  fowl  and  none  is  to  be  expected,  since  the  color  of  the  mandibles 
is  the  same  in  each  sex  of  Leghorns.  In  Rouens  the  upper  mandible 
of  the  male,  both  normal  and  castrated,  is  uniform  greenish  yellow,  in 
the  normal  female  dark  greenish  with  a  large  central  black  area.  In 
the  cross-bred  birds  the  mandibles  may  be  yellow  in  each  sex.  In 
Gray  Calls  (Mallard  in  plumage  color)  the  mandible  of  the  male  is 
greenish  yellow  with  a  blotch  like  that  of  the  female.  In  the  castrated 
female  the  central  blotch  remains,  but  the  dark  greenish  color  of  the 
margin  disappears,  leaving  these  parts  yellow.  Castration,  then,  is  with- 
out influence  on  the  male's  mandible  color,  but  removal  of  the  ovaries 
results  in  the  disappearance  of  certain  pigments  from  the  mandible  of 
the  female,  regardless  of  the  age  at  which  the  operation  is  performed. 

The  newly  hatched  ducklings  are  alike  in  the  color  of  the  mandible, 
which  is  almost  black.  During  ontogeny  that  of  the  male  lightens  up 
uniformly  until  the  adult  color  is  reached ;  that  of  the  female,  however, 
lightens  in  certain  regions  only,  corresponding  to  the  pattern  described. 
In  one  lot  of  ducklings  a  month  old  the  differences  hi  mandible  color 
were  already  apparent.  Probably  it  will  be  necessary  in  operating  to 
anticipate  such  changes  if  a  modification  of  the  mandible  color  is  to  be 
secured,  but  thus  far  attempts  to  ovariotomize  ducklings  a  week  or  two 
of  age  have  failed.  We  are  unable,  consequently,  to  deternime  the 
exact  relationship  between  the  ovary  and  the  blotch  in  the  female's 
mandible.  It  is  hazardous  to  assume,  from  Analogy  with  other  char- 
acters, that  the  female  mandible  color  is  really  dependent  on  the  ovary, 
but  that  its  pigments  have  been  deposited  in  an  unchangeable  state,  com- 
parable with  that  in  a  fully  formed  feather.  Instead  it  is  possible  that 
it  is  a  unit  character  inherited  according  to  some  definite  but  unknown 
scheme.  In  Gray  Call  ducks,  as  pointed  out,  the  male  has  the  central 
blotch  as  well  as  the  female.  The  male  Rouen,  exceptionally,  may 
have  the  ridge  of  the  mandible  darker  than  the  rest.  Since  the  "  Stand- 
ard of  Perfection"  calls  for  the  mandible  color  described  above,  it 
becomes  more  probable  that  the  blotch  represents  a  separate  unit 
character. 

EFFECT  ON  SIZE. 

It  has  long  been  known  that  the  male  mammal  and  bird,  when  cas- 
trated young  enough,  grow  larger  than  intact  individuals.  This  is  due  in 
part  to  the  continued  growth  of  the  epiphyses  of  the  long  bones,  though 
at  the  same  time  there  is  a  general  increase  in  size.  The  present  set 
of  experiments  has  not  been  of  sufficient  extent,  nor  has  the  stock  been 
sufficiently  homogeneous  in  respect  to  weight,  to  give  average  results 
of  any  value  whatsoever.  That  is,  the  variation  among  normals  is  so 
great  that  a  comparison  with  the  few  castrated  individuals  might  be 


42  GONADECTOMY   IN   RELATION  TO   THE    SECONDARY 

misleading.  Nevertheless,  some  general  statements  may  be  made- 
While  the  Brown  Leghorn  capons  are  obviously  somewhat  larger  than 
the  normal  male,  such  a  condition  is  not  so  obvious  in  any  of  the  cas- 
trated drakes,  although  the  weights  indicate  some  increase  in  size. 

The  castrated  ducks  approximate  the  size  of  the  normal  female. 
The  castrated  pullets,  too,  remain  about  the  same  size  as  normal  pul- 
lets, although  they  seem  relatively  small.  The  apparent  lack  of  size 
is  due  to  the  fact  that  the  legs  remain  small,  like  those  of  the  hen,  while 
the  plumage  develops  like  that  of  the  cock,  thus  producing  a  small- 
bodied,  short-legged  bird  quite  different  from  the  cock  or  capon  with 
large  frame.  All  that  can  be  said  of  the  size  relations  at  present  is 
that  the  body-size  of  the  castrated  pullet  does  not  exceed  that  of  her 
normal  sister.  The  shanks,  likewise,  though  spurred,  are  of  the  same 
size  as  those  of  the  normal  female. 

EFFECT  ON  BEHAVIOR. 

Completely  castrated  individuals  of  all  kinds  are  on  the  whole  nega- 
tive in  behavior  as  compared  with  normal  adults.  The  behavior  of 
castrates  corresponds  rather  closely  to  that  of  young  birds  shortly 
before  they  become  mature.  The  birds  eat,  drink,  and  move  about 
rather  quietly.  The  capons  do  not  ordinarily  crow  or  pay  any  particu- 
lar attention  to  the  hen.  They  are  not  pugnacious,  and  if  attacked  will 
not  often  fight.  The  poullards  never  visit  the  nests,  never  "sing"  or 
cackle,  show  none  of  the  normal  female  sexual  reactions,  and  few  or 
none  of  the  male's.  The  castrated  ducks  are  neither  more  nor  less  noisy 
than  their  mates,  but  sexual  behavior  is  wanting.  Normal  drakes 
sometimes  attempt  to  tread  castrated  females  (Type  I  as  well  as  Type 
II)  that  are  kept  in  the  same  pen.  The  duck,  however,  attempts  to 
escape,  so  that  the  male  gets  little  satisfaction.  Evidently  the  color 
loses  any  value  it  may  have  had  as  a  recognition  mark.  On  the  other 
hand,  castrated  females  introduced  into  a  strange  pen  have  been 
treated  at  first  as  a  strange  male.  It  is  clear,  too,  from  the  behavior 
of  hens  when  a  poullard  is  introduced  into  a  pen  which  contains  no 
male  that  they  regard  the  poullard  as  a  male.  The  poullard,  however, 
does  not  behave  as  a  male,  but  is  rather  indifferent,  though  in  one  test 
the  bird  was  extremely  pugnacious  and  attacked  every  hen  that 
approached. 

EFFECT  ON  ACCESSORY  ORGANS  OF  REPRODUCTION. 
Most  of  the  birds  operated  on  are  still  alive,  so  that  general  state- 
ments only  can  be  made  regarding  these  organs.  Usually  the  vas 
deferens  in  both  castrated  drakes  and  capons  can  not  be  found  unless 
there  has  been  a  considerable  regeneration  of  spermatogenic  tissue;  but 
occasionally  it  remains  visible  as  a  thin  strand  of  tissue  with  few  or  no 
convolutions.  The  papillae  of  the  capon  also  have  not  been  found,  but 
as  these  are  very  small  in  the  cock,  such  a  result  is  not  surprising.  In 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC  BIRDS.  43 

drakes,  the  penis  has  always  been  found,  sometimes  rather  smaller 
and  more  flaccid  than  usual,  but  otherwise  essentially  the  same  as  that 
of  an  intact  drake. 

In  the  castrated  female  the  oviduct  has  always  been  found.  It  is 
larger  than  that  of  the  young  chick,  corresponding  in  its  dimensions  to 
the  increased  size  of  the  bird,  but  otherwise  is  entirely  infantile.  In 
this  respect  it  is  like  the  comb  of  the  capon.  The  increase  in  absolute 
size  of  oviduct  is  mainly  in  length,  with  a  slight  increase  in  width,  quite 
like  that  of  a  young  pullet  prior  to  the  enlargement  of  the  oviduct  hi 
anticipation  of  laying. 

EFFECT  ON  THE  BURSA  FABRICII. 

This  is  not  a  secondary  sexual  character,  but  like  the  thymus  is 
essentially  an  organ  of  the  young  and  undergoes  involution  at  or  near 
maturity.  As  slight  attention  was  paid  to  it  until  its  persistence  was 
noticed  in  two  completely  castrated  drakes,  little  can  be  said  of  it  now. 
In  incompletely  castrated  males  it  can  not  be  found.  Future  observa- 
tions may  show  that  some  intimate  relation  exists  between  it  and  the 
primary  organs  of  reproduction. 

OCCURRENCE  OF  CHARACTERS  OF  ONE  SEX   IN  INDIVIDUALS  OF 
THE  OPPOSITE  SEX  THAT  ARE  OTHERWISE  NORMAL. 

MALE  CHARACTERS  IN  THE  OTHERWISE  NORMAL  FEMALE. 

The  most  conspicuous  of  these  characters  are  spurs  which  occur  in 
some  females  that  otherwise  are  apparently  normal.  In  plate  vn,  B, 
are  shown  the  shanks  of  a  White  Leghorn  hen  now  8  years  old.  The 
spurs,  while  somewhat  more  slender  than  those  of  a  cock,  i.  e.,  in 
proportion  to  her  shanks,  are  otherwise  quite  as  male-like  as  could  be 
wished.  In  other  respects  the  bird  is  entirely  female  in  character,  even 
her  head  furnishings  being  feminine.  She  has  laid  well  and  her  eggs 
have  hatched  well.  This  bird  was  about  2  years  old  when  the  spurs 
were  first  noticed.  At  that  time  they  were  as  well  developed  as  in 
cocks  of  the  same  age.  Another  hen,  No.  1055,  related  to  the  first, 
also  has  a  fine  pair  of  spurs.  They  appeared  when  the  bird  was  6 
months  of  age  as  blunt  stubs  exactly  like  those  of  a  cockerel,  and  by 
the  time  she  was  a  year  old  they  had  enlarged  and  become  as  pointed  as 
those  of  any  male  of  the  same  age.  Both  these  birds  have  been  bred 
from,  and  a  hundred  or  more  chicks  hatched,  but  because  of  certain 
circumstances  few  of  the  pullets  have  been  kept  sufficiently  long  to 
develop  spurs  and  these  appeared  in  only  one  of  the  few  kept.  But 
the  fact  that  spurred  females  appear  in  large  numbers  in  some  strains 
indicates  that,  at  bottom,  the  spurs  in  the  uncastrated  female  depend 
upon  some  hereditary  factor  or  combination  of  factors. 

The  comb  and  wattles  of  some  females  are  often  very  large,  giving 
the  bird  a  masculine  appearance.  In  Leghorns  and  other  large-combed 
breeds  the  large  combs  in  the  female  are  not  considered  masculine, 


44  GONADECTOMY   IN   RELATION   TO   THE   SECONDARY 

even  when  the  lop  is  absent.  If,  however,  a  pullet  with  an  erect  comb  of 
similar  size  appears  in  a  flock  of  Plymouth  Rocks,  she  looks  masculine. 
However,  the  proportions  of  the  comb  are  usually  unlike  those  of  a 
male,  and  it  also  seems  probable  that  if  the  bird  had  been  a  male  the 
comb  would  have  been  several  times  the  size  it  actually  attained.  In 
other  words,  such  birds  are  simply  large-combed  but  not  masculine- 
combed  females. 

In  Mediterranean  breeds  the  comb  of  the  male  is  erect,  that  of  the 
female  lops.  Females,  however,  frequently  occur  with  erect  combs, 
which,  however,  are  of  female  size  and  proportions.  In  some  males 
there  is  a  tendency  for  the  comb  to  lop,  particularly  when  young, 
though  it  never  does  so  in  quite  the  same  fashion  as  it  lops  in  the 
female.  While  the  comb  of  the  female  never  lops  after  complete  cas- 
tration, the  comb  of  the  young  capon  lops  sometimes,  like  that  of  the 
young  male.  There  is  no  reason,  however,  to  believe  that  the  lop  of  the 
adult  female  and  that  of  the  young  male  are  due  to  the  same  causes. 
The  lop  observed  in  the  comb  of  young  males  usually  (but  not  always) 
appears  due  to  lack  of  stamina  or  to  some  environmental  causes,  such 
as  an  injury. 

The  exposed  surface  of  the  secondaries  constitutes  the  wing  bay.  In 
the  female  of  those  races  where  there  is  a  sex  differential  coloration  of 
the  body  this  area  is  stippled.  In  Brown  Leghorns  the  stippling  is  light 
brown  on  a  dark-brown  ground-color.  In  the  male  it  is  a  solid 
color — a  uniform  red  in  the  Leghorns.  While  the  stippled  condition 
may  be  transitory  in  the  young  male,  it  has  not  been  observed  in  the 
adult,  either  normal  or  castrated.  In  some  cross-bred  females  belong- 
ing to  the  writer,  the  wing  bay  of  the  females  is  a  solid  color  and  its 
feathers  would  readily  pass  for  a  male's  feathers  from  that  region.  A 
condition  of  this  region,  intermediate  between  the  male  and  the  female, 
often  appears  in  Brown  Leghorn  females,  and  associated  with  it  is  a 
condition  known  as  " brick"  by  the  fanciers.  The  brick  is  a  reddish 
color  of  the  wing-bow  region,  exactly  that  region  which  in  the  male  is 
red.  Its  appearance  strongly  suggests  a  heterozygous  condition,  but 
no  breeding  tests  have  been  carried  out. 

In  ducks,  so  far  as  I  know,  the  only  male  character  that  appears  in 
otherwise  normal  females  is  the  neck  ring,  though  it  is  reported  that 
normal  females  sometimes  develop  the  curled  tail  feathers  of  the  male. 
In  one  instance  the  neck  ring  appeared  when  the  duck  (a  Rouen  with 
typical  female  plumage)  was  less  than  a  year  old,  but  it  is  not  known 
whether  the  duck  laid  or  not.  In  hybrid  females  there  are  several  types 
of  neck  rings,  among  them  one  like  that  of  the  male  Rouen  or  Mallard. 
On  the  other  hand,  some  hybrid  males  show  no  trace  of  a  neck  ring. 
One  or  two  females  of  this  race  lacking  neck-rings  have  been  castrated 
and  they,  too,  have  not  developed  any  ring,  though  otherwise  they 
have  been  among  the  most  perfectly  male-plumaged  individuals. 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  45 

On  the  other  hand,  there  are  male  characters  which  never  seem  to 
occur  in  the  unaltered  female,  such  as  male  saddle  feathers,  sickle 
feathers,  black  breast  in  Brown  Leghorns  (though  self-colored  brown 
breasts  occur,  the  individual  feathers  of  which  are  stippled),  while  hi 
ducks  vermiculated  feathers,  body  pattern,  etc.,  syrinx,  bill  color,  etc., 
have  not  been  observed  in  the  normal  female.  Brandt,  however,  cites 
instances  of  fertile  cock-feathered  females.  In  general,  then,  it  seems 
highly  probable  that  some  intimate  relation  exists  between  the  germinal 
constitution  of  the  female  and  the  appearance  in  the  normal  individual 
of  certain  characters  usually  found  only  in  the  male.  Also,  it  is  inter- 
esting to  note  that  these  characters  appear  in  the  ducks  of  Type  II, 
described  above.  Obviously,  there  is  some  close  relationship  between 
the  gametic  constitution  of  an  individual  and  the  internal  secretion  of 
the  germ  glands. 

FEMALE  CHARACTERS  IN  THE  OTHERWISE  NORMAL  MALE. 

Instances  of  the  occurrence  of  female  characters  in  males,  strictly 
comparable  to  those  just  described  for  the  female,  are  uncommon  or 
wholly  lacking.  It  has  already  been  shown  that  the  only  character  of 
this  sort  among  capons  is  the  brooding  instinct.  One  reason  for  the 
non-occurrence  of  such  cases  is  found  in  the  few  characters  that  it  is 
impossible  to  confuse  with  juvenile  conditions.  Brandt  records  only  two 
or  three  doubtful  instances  of  this  sort  among  a  large  number  where 
females  exhibited  male  characters.  On  the  other  hand,  when  female 
characters  occur  in  the  male  they  either  form  part  of  a  normal  cycle, 
such  as  the  winter  plumage  of  the  bobolink,  or  the  laterals  in  the  summer 
plumage  of  the  drake,  or  they  are  breed  characters,  such  as  hen  feather- 
ing, discussed  below.  We  may,  perhaps,  distinguish  two  categories  of 
secondary  sexual  characters,  viz,  those  absolutely  dependent  on  the 
internal  secretion  of  the  gonad  and  those  partially,  at  least,  independent, 
and  if  this  be  true  then  those  male  characters  occurring  sporadically  in 
females  otherwise  normal  are  in  essentially  the  same  class  as  the  oc- 
currence of  female  characters  in  the  otherwise  normal  male. 

HEN-FEATHERED  MALES. 

These  birds  are  of  great  interest  from  several  standpoints.  The 
classical  example  is  that  of  the  Seabright  bantams,  yet  it  is  stated  in 
the  history  of  this  breed  that  the  hen-leathering  originated  outside. 
Doubtless,  hen-feathered  males  have  long  existed.  They  frequently 
occur  as  " sports"  among  Hamburgs,  while  among  Campines  two 
types  of  males  are  recognized,  the  English  or  hen-feathered  and  Belgian 
or  normal  type.  These  hen-feathered  birds  are  fertile,  though  the 
statement  has  been  made  for  Seabrights  that  those  which  are  most 
strongly  hen-feathered  are  inclined  to  be  sterile.  Possibly  the  reason 
is  to  be  found  in  an  inherited  condition  of  sterility.  Hen-feathered 
males  have  their  other  male  characters  well  developed.  However,  the 


46  GONADECTOMY   IN   RELATION   TO    THE    SECONDARY 

writer  has  never  seen  a  hen-feathered  male  in  a  race  where  the  females, 
were  of  the  Brown  Leghorn  or  Dark  Brahma  type  of  color.  Whether 
or  not  the  males  of  such  a  race  would  take  the  female's  color  on  becom- 
ing hen-feathered  is  unknown.1  In  Hamburgs,  Seabrights,  and  Cam- 
pines  the  normal  male  is  colored  like  the  female  in  some  parts  of 
of  the  body  at  least,  a  color  which  is  often  very  like  that  of  the  juvenile 
male,  so  that  it  is  impossible  to  ascertain  whether  or  not  the  coloration 
of  hen-feathered  males  is  female  or  not.  In  regard  to  the  shape  of  the 
feathers,  a  more  definite  statement  can  be  made.  The  shape  of  the 
feathers  of  the  hen-feathered  male  is  exactly  like  those  of  the  juvenile 
coat  of  the  male,  but  as  these  are  also  the  same  shape  as  those  of  the 
female,  they  furnish  us  no  proof  of  the  assumption!  of  a  female  character 
by  the  male.  In  addition  to  normal  male-feathered  cocks  in  these  races, 
I  have  seen  a  third  type,  in  Campines,  in  which  part  of  the  feathers  of 
the  regions  under  discussion  are  male,  while  the  rest  are  juvenile  (or 
female) .  Such  birds  always  looked  ragged  and  are  very  suggestive  of 
the  condition  of  young  males  at  the  molt  between  the  juvenile  and  male 
plumage.  According  to  some  experiments  that  have  been  reported  by 
various  observers,  it  is  certain  that  the  hen-feathered  condition  is  a 
definitely  inheritable  character. 

Since  the  castrated  male  in  normal  races  develops  normal  plumage, 
and  since  the  hen-feathered  character  is  undoubtedly  an  inheritable 
character,  it  seems  better  to  refer  the  condition  to  a  factor  which  alters 
the  form  of  plumage.  Perhaps  it  is  an  inhibitor.  Naturally,  since 
the  female  already  has  the  same  form  of  feathers,  she  will  not  exhibit 
any  modifications.  If  this  had  been  the  normal  feathering  of  Gallus 
bankivus,  as  it  is  in  the  turkey  or  duck,  the  appearance  of  a  new  form 
of  feather  in  the  male  alone  would  constitute  a  new  secondary  sexual 
character.  The  assumed  primitive  male,  however,  would  not  be  hen- 
feathered.  Looking  at  it  from  this  standpoint,  it  is  evident  that  we 
must  give  due  regard  to  the  part  played  by  inheritance.  At  present, 
I  believe  we  are  unable  to  point  to  any  female-like  character  in  males 
that  is  not  also  juvenile.2 

INHERITANCE  OF  SECONDARY  SEXUAL  CHARACTERS. 

Disregarding  for  the  moment  Type  II,  it  is  apparent  that  the  inherited 
base  for  the  secondary  sexual  characters  in  each  sex  is  the  same — that 
is,  the  characters  in  each  sex,  except  for  the  secretion  of  the  ovary, 
would  be  alike.  In  other  words,  there  is  no  problem  of  the  mode  of 
inheritance  of  secondary  sexual  characters  in  birds  such  as  there  is  in 
insects,  where  these  characters  are  independent  of  the  gonads.  The 
secondary  sexual  characters  are  inherited  in  exactly  the  same  fashion 

1Morgan,  1915,  has  found  that  such  males  take  on  the  female's  color. 

2Since  this  section  was  written,  Morgan,  1915,  has  shown  that  the  hen-feathered  condition  in 
the  male  is  due  to  an  internal  secretion  of  the  testes. 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  47 

as  many  other  characters  which  are  exactly  alike  in  each  sex.  The 
sole  difference  lies  in  the  ovary.  Moreover,  the  genetic  factors  that 
are  transmitted,  if  expressed  in  terms  of  their  somatic  results  in  the 
absence  of  the  ovary,  are  the  male  characters.  In  this  connection  it 
is  important  to  note  that  the  castrated  females  have  always  taken  the 
characters  of  the  male  of  the  race  to  which  they  belong.  This  has 
been  particularly  noticeable  among  the  cross-bred  ducks,  where  there 
are  several  distinct  types.  In  crosses,  then,  each  sex  transmits  the 
same  set  of  genes,  while  the  resulting  characters  are  modified  by  the 
ovary  into  the  proper  female  somatic  characters.  Unfortunately, 
however,  such  a  simple  solution  of  the  breeding  problem  is  not  of 
universal  applicability.  The  presence  of  the  Type  II  female,  together 
with  certain  characters,  such  as  mandible  color,  stands  in  the  way. 
Here  recourse  was  made  to  the  genetic  constitution  of  the  bird  to 
explain  their  appearance.  Attractive  as  the  ovarian-secretion  explana- 
tion may  be,  it  does  not  entirely  do  away  with  the  need  for  an  explana- 
tion of  the  inheritance  of  secondary  sexual  characters. 

The  mode  of  inheritance  of  the  internal  secretion  is  a  different  thing 
from  the  inheritance  of  secondary  sexual  characters  as  such.  Obviously 
it  is  closely  connected  (coupled  or  linked,  if  you  like)  with  the  inheri- 
tance of  sex  itself;  so  closely  indeed  that  the  two  can  not  be  separated 
by  any  means  now  available.  We  must  for  the  present  treat  it  as  if  it 
were  "femaleness,"  unless  the  following  hypothesis  seems  more  desir- 
able. The  genes  for  the  secretion  may  be  considered  to  be  inherited 
independently  of  the  sex  genes,  but  just  as  the  Miillerian  duct  disap- 
pears in  the  male,  so  the  mechanism  for  the  production  of  the  secretion 
may  also  disappear  in  this  sex.  Such  a  scheme  does  away  with  the 
use  of  sex-linked  inheritance  in  this  connection. 

IS  THE  FEMALE  BIRD  A  SUPPRESSED  HERMAPHRODITE? 

A  true  hermaphrodite  possesses  both  ovary  and  testes  with  their 
respective  products,  ova  and  spermatozoa.  There  is  no  direct  evidence, 
then,  that  the  female  fowl  is  a  potential  true  hermaphrodite,  since  sper- 
matozoa have  not  yet  been  observed  in  castrated  females.  However, 
the  presence  of  certain  accessory  organs  of  reproduction  following 
ovariotomy  points  strongly  in  this  direction.  The  anlagen  of  both  vas 
deferens  and  oviduct  occur  in  each  sex,  and  so  each  sex  might  be  con- 
sidered to  be  a  potential  hermaphrodite.  It  is  certain,  moreover,  that 
the  Miillerian  duct  completely  disappears  in  the  male,  but  apparently 
the  Wolffian  duct  and  body  may  not  always  degenerate  in  the  female. 
There  is  good  evidence  from  breeding  that  the  female  is  a  sex  hetero- 
zygote,  though  the  cytological  evidence  in  this  respect  is  negative, 
resting  on  the  failure  of  Boring's  and  Pearl's  work  to  substantiate 
Guyer's  report  of  an  accessory  chromosone  (sex  heterozygotism)  in  the 
male.  Though  in  many  instances  there  is  indisputable  evidence  that 
sex  is  determined  at  the  moment  of  fertilization,  there  is  other  evidence 


48  GONADECTOMY   IN   RELATION   TO   THE   SECONDARY 

that  sex,  in  the  sense  of  the  separation  of  male  from  female  sex  cells,  may. 
be  determined  after  fertilization;  for  example,  in  normal  hermaphro- 
dites, such  as  Helix,  Lumbricus,  etc.,  and  the  many  instances  among 
plants.  Among  the  latter,  many  regions  that  normally  produce  macro- 
or  micro-spores  may,  under  a  suitable  stimulus  produce  the  other  kind. 
Neither  the  assumption  of  male  plumage  by  the  female  nor  the  develop- 
ment of  the  accessory  reproductive  organs  need  be  considered  evidence 
that  the  female  is  a  suppressed  hermaphrodite,  because  the  secretion  of 
the  ovary  clearly  controls  their  development.  On  the  other  hand,  it  is 
clearly  proven  that  the  female  is  a  suppressed  pseudo-hermaphrodite. 

If  there  is  any  basis  in  fact  that  the  normal  female  is  a  suppressed 
hermaphrodite,  then,  since  there  is  no  reason  to  believe  that  the  male 
is  an  hermaphrodite,  those  avian  hermaphrodites  that  occur  in  nature 
must  arise  through  a  failure  of  the  mechanism  for  the  suppression  of 
the  male  in  normal  females. 

Unless  and  until  ovariotomy  should  be  found  to  result  in  actually 
converting  a  female  into  a  male  with  spermatozoa,  thus  demonstrating 
that  the  female  is  a  suppressed  hermaphrodite,  the  effects  of  castration 
on  the  secondary  sexual  characters  can  not  be  said  to  have  a  bearing 
on  the  problems  of  sex  determination.  They  demonstrate  rather  the 
existence  of  a  mechanism  for  the  control  of  the  secondary  sexual  char- 
acters that  is  so  closely  associated  with  certain  parts  of  the  mechanism 
for  the  determination  of  sex  that  the  two  go  together,  except,  perhaps, 
in  races  of  the  Seabright  type.1  The  association,  however,  throws  no 
new  light  on  the  mechanism  by  which  sex  is  determined,  unless  we  wish 
to  extend  the  idea  of  internal  secretions  by  assuming  that  all  individ- 
uals are  hermaphroditic  and  that  at  some  period  after  fertilization  a 
mechanism  comes  into  operation  that  partially  or  wholly  suppresses 
the  opposite  sex.  It  is  conceivable  that  the  secretions  of  certain  cells 
in  the  embryo  may  determine  which  class  of  primitive  ova  develops. 
The  result  would  be  the  same,  of  course,  as  if  the  usual  sex  scheme  is 
followed,  with  this  difference,  that  the  determining  mechanism  is  not  in 
itself  sex.  Such  a  scheme  would  account  for  the  appearance  of  the 
Miillerian  and  Wolffian  ducts  and  associated  parts  in  all  embryos. 

THE  RELATION  BETWEEN  BREEDING  AND  GONADECTOMY. 

The  results  obtained  from  gonadectomy  have  considerable  bearing 
of  a  practical  nature  on  inheritance  studies  in  poultry.  We  need  no 
longer  erect  separate  categories  for  characters  that  appear  in  one  sex 
only,  but  may  classify  a  given  character  in  the  female  with  the  corre- 
sponding character  in  the  male,  even  though  the  two  characters  actu- 
ally appear  very  unlike.  These  remarks  apply  naturally  only  to  those 
characters  that  are  actually  modified  by  the  internal  secretion  of  the 
ovary,  while  due  regard  must  be  paid  to  the  exceptions  noted  where 
the  castrated  female  does  not  develop  a  normal  male  plumage. 

1See  note  2  page  46. 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  49 

DARWIN'S  AND  WALLACE'S  THEORIES  OF  THE  ORIGIN  OF 
SECONDARY  SEXUAL  CHARACTERS. 

Both  of  these  theories  assume  that  the  difference  between  the  sexes 
has  arisen  through  selection — natural  selection  according  to  Wallace, 
sexual  selection  according  to  Darwin.  Birds,  in  particular,  have  fur- 
nished illustrations  in  support  of  each  theory.  Natural  selection  is 
assumed  to  have  operated  through  the  survival  of  those  females  that 
were  more  protectively  colored  than  their  mates.  The  theory  of  sexual 
selection  assumes,  on  the  other  hand,  that  the  males  acquired  their 
present-day  colors  in  response  to  selection  on  the  part  of  the  females, 
which  chose  the  more  highly  colored  males.  According  to  Darwin's 
theory  the  start  was  made  from  a  dull-colored  monomorphic  species, 
an  assumption  that  is  not  in  accord  with  the  nature  of  the  female  as 
shown  by  castration,  since  the  brilliant  male  colors  are  merely  sup- 
pressed in  her.  The  only  possible  effect  of  selection,  then,  would  be 
the  uncovering  of  a  condition  already  present.  But,  by  hypothesis, 
this  condition  did  not  pre-exist. 

Wallace's  theory,  starting  also  with  a  probably  dull-colored  mono- 
morphic species,  is  in  partial  agreement  with  the  results  of  castration. 
It  must  be  modified  by  assuming  that  natural  selection  acted  indirectly 
through  the  development  of  an  internal  secretion  of  the  ovary  pari 
passu  with  increased  brilliancy  of  the  male  rather  than  on  the  charac- 
ters themselves.  Since,  however,  the  female  possesses  the  same  poten- 
tialities as  the  male,  the  start  may  have  been  from  a  highly  colored 
form  rather  than  the  reverse. 

NATURE  AND  MODE  OF  THE  OVARIAN  SECRETION. 

The  adjustment  of  the  ovarian  secretion  to  the  characters  it  modi- 
fies is  very  close,  as  shown  by  the  fact  that  the  male  characters  produced 
in  a  given  female  are  like  those  of  the  corresponding  male.  This  must 
mean  that  the  large  element  in  determining  the  result  is  the  heredity 
basis  and  not  the  secretions.  From  this  we  may  conclude  that  the 
secretion  on  the  whole  is  relatively  simple  and  probably  of  uniform 
nature.  If  the  secretion  were  composed  of  many  substances,  one  to 
produce  each  effect  involved,  such  as  the  change  from  a  vermiculated 
feather  to  penciled,  from  a  gray  and  white  to  a  black  and  brown,  the 
resulting  complexity  would  be  so  great  that  one  would  not  anticipate 
any  such  close  coordination  as  actually  results.  For  purposes  of  illus- 
tration we  may  assume  that  the  ovarian  secretion  is  simple,  producing 
its  effect  by  oxidation  or  some  other  simple  process.  The  sort  of  result 
produced  by  oxidation,  of  course,  depends  upon  the  substance  that  is 
oxidized. 

From  another  standpoint,  the  question  may  be  raised  as  to  whether 
the  secretion  should  be  considered  as  a  modifier  or  an  inhibitor.  If  it 
be  assumed  that  it  is  a  modifier,  only  one  genetic  basis  need  be  assumed 


50  GONADECTOMY   IN   RELATION  TO   THE   SECONDARY 

for  each  sex,  i.  e.,  the  genetic  basis  that  is  responsible  for  the  male 
secondary  sexual  characters.  The  modifier  changes  over  the  male 
characters  into  the  female  characters.  On  the  other  hand,  an  inhibi- 
tion requires  the  assumption  of  two  genetic  bases  (factors  or  group  of 
factors),  one  responsible  for  the  male  secondary  sexual  characters,  the 
other  for  the  female.  In  the  absence  of  the  ovarian  secretion,  the  male 
characters  appear.  If  the  secretion  be  present,  it  inhibits  the  male 
characters  and  allows  the  female  characters  to  appear.  In  some 
respects  it  is  simpler  to  assume  that  the  internal  secretion  actually 
changes  over  the  male  characters  into  female  because  only  one  genetic 
basis  need  be  assumed.  The  back,  wing-bow,  and  saddle  feathers  in 
particular  fit  in  with  such  an  assumption.  In  the  male  the  barbs  lack 
the  barbules  on  their  distal  half,  i.  e.,  are  bristle-like,  though  they  are 
present  in  the  female.  In  Leghorn  males  the  juvenile  feathers  of  this 
region  have  barbules,  but  they  disappear  on  the  adult  feathers,  though 
in  other  races  individuals  often  occur  which  lack  the  juvenile  coat  in 
this  region,  growing  adult  feathers  directly  from  the  down  follicles. 
Something  must  prevent  the  development  of  the  barbules  in  the  adult; 
therefore,  if  the  ovarian  secretion  is  an  inhibitor  merely,  we  have  an 
inhibition  of  an  inhibition.  The  inhibition  of  barbule  development  in 
the  male  must  be  germinal,  for  it  is  certainly  not  testicular,  since  after 
orchidotomy  the  barbules  do  not  develop. 

In  the  last  analysis  the  effect  of  the  ovarian  secretion  comes  down 
to  its  effect  on  the  cells,  either  the  cytoplasm  or  nucleus,  but  if  the 
control  of  the  direction  of  developments  lies  in  the  chromosomes,  then 
the  influence  of  this  secretion  must  be  exerted  upon  these  through  the 
intermediation  of  the  cell  protoplasm. 

In  the  formation  of  the  various  colors  it  is  possible  to  conceive  of 
a  mechanism  whereby  the  internal  secretions  combining  with  an 
enzyme,  or  possibly  acting  as  such,  are  able  to  change  the  color.  Such 
an  explanation,  however,  seems  insufficient  to  account  for  the  arrange- 
ment of  cells  in  the  feather,  the  number  produced,  and  whether  or  not 
they  have  processes  (hamulse). 

We  may,  however,  conceive  that  the  presence  of  the  ovarian  secretion 
in  the  body  fluids  surrounding  the  cells  influences  their  development 
in  much  the  same  way  that  modifications  of  characteristics  are  induced 
in  organisms  by  the  environment.  The  secretions,  indeed,  must  be 
considered  part  of  the  environment  of  each  cell.  The  cells,  how- 
ever, respond  only  when  in  a  growing,  or,  at  least,  active  condition. 
Feathers,  for  example,  change  color  only  at  a  molt,  so  that  a  bird 
might  be  castrated  and  never  change  color  for  nearly  a  year.  In  this 
respect  the  secretion  is  like  all  other  environmental  factors. 


SEXUAL   CHARACTERS   OF   SOME   DOMESTIC   BIRDS.  51 

RELATION  BETWEEN  THE  GONADS  AND  THE  SECONDARY  SEXUAL 
CHARACTERS  IN  OTHER  GROUPS. 

The  influence  exerted  by  the  gonads  on  the  secondary  sexual  char- 
acters varies  from  group  to  group.  In  insects,  the  secondary  sexual 
characters  are  independent  of  the  gonads.  In  certain  crustaceans 
conditions  are  the  reverse  of  those  found  in  birds.  In  mammals, 
removal  of  the  testes  produces  an  effect  very  similar  to  that  on  the  male 
bird .  The  female,  however,  undergoes  very  little  change  in  her  secondary 
sexual  characters.  Steinach,  however,  has  shown  that  by  transplanting 
ovaries  into  the  castrated  male — rat  or  guinea-pig — he  becomes  femin- 
ized. Bresca  found  in  Triton  that  the  crest  of  the  tail  did  not  develop 
after  castration,  while  Nussbaum  found  for  the  frog  that  the  thumb  pads 
failed  to  develop,  though  Smith  secured  results  opposed  to  Nussbaum' s. 

On  the  whole,  the  relation  between  the  gonads  and  the  secondary 
sexual  characters  appears  to  be  specific  and  not  general.  Although 
more  striking,  their  relation  is  essentially  of  the  same  order  as  other 
morphogenetic  secretions,  such  as  that  of  the  thyroid.  Indeed,  the 
morphogenetic  activity  of  the  gonads  is  by  no  means  confined  to  the 
secondary  sexual  characters,  but  produces  other  well-known  effects. 

SUMMARY. 

1.  If  the  ovary  of  a  domestic  bird  be  removed  completely,  many  of 
the  secondary  sexual  characters  of  the  male  appear.     Some  individuals 
become  nearly  complete  replicas  of  the  male,  others  imperfect  imita- 
tions of  the  male. 

2.  If  the  testes  be  removed,  the  majority  of  the  secondary  sexual 
characters  of  the  male  develop,  though  a  few  may  remain  in  an  infantile 
condition. 

3.  Castrated  drakes  lose  the  power  of  developing  the  summer 
plumage. 


52  LITERATURE   CITED. 

LITERATURE  CITED. 

ANCEL  and  BOUIN.     1913.    Sur  la  signification  de  la  glande  interstitiale  du  testicelle  embry- 

onaire.    C.  R.  Soc.  Biol.  I,  V.   Also  other  papers  by  same  authors. 
ALLEN,  B.  M.     1905.    The  embryonic  developnemt  of  the  rete-cords  and  sex-cords  of 

Chrysemys.     Amer.  Jour,  of  Anat.,  vol.  5,  pp.  79-94. 
BORING,  A.,  and  R.  PEARL.     1914.    The  odd  chromosome  in  the  spermatogenesia  of  the 

domestic  chicken.    Journ.  Exp.  Zool.,  vol.  16. 
BRANDT,  A.     1889.    Anatomisches  und  Allgemeines  iiber  die  eogenannte  Hahnfedrigkeit 

und  iiber  anderweitige  Geschlechtsanomalien  bei  Vogeln.  Zeit.  f .  wiss.  Zool.,  Bd.  48. 
BRESCA,  G.     1910.    Experimentelle  Untersuchungen  iiber  die  sekundaren  sexualcharactere 

der  Tritonen,  Arch.  Exp.  Org.,  Bd.  xxix. 
DARWIN,  CHARLES.  1871.  The  descent  of  man. 
FITZSIMONS,  F.  W.  1912.  A  hen  ostrich  with  the  plumage  of  a  cock.  Agri.  Journ. 

Univ.  South  Africa,  vol.  4. 
FOGES,  A.     1898.     Zur  Hodentransplantion  bei  Hahnen.     Zentralb.  f .  Phys. 

1902.    Zur  von  den  secundaren  Geschlechtscharacteren.   Arch,  f .  ges.  Phys.,  Bd.  93. 

GOODALE,  H.  D.     1913.     Castration  in  relation  to  the  secondary  sexual   characters  of 

Brown  Leghorns.    Amer.  Nat.,  XLVII,  pp.  159-169. 

1916.     Further  developments  in  ovariotomized  fowl.     Biol.  Bull.,  vol.  xxx. 

GUYER,  M.  F.     1909.     Spermatogenesis  of  the  domestic  chicken.    Anat.  Anz.,  Bd.  34. 
GUTHRIE,  C.  C.     1910.     Survival  of  engrafted  tissues.     Journ.  Exp.  Med.,  vol.  xn. 
HALBAN,  J.     1903.     Die  Entstehung  der  Geschlechtscharactere.    Arch.  f.  Gynk.,  Bd.  LXX. 
LILLIE,  F.  R.     1908.    The  development  of  the  chick. 

MARSHALL,  F.  H.  A.     1910.     Physiology  of  reproduction. 

MORGAN,  T.  H.  1915.  Demonstration  of  the  appearance  after  castration  of  cock  feather- 
ing in  a  hen-feathered  cockerel.  Proc.  Soc.  Exp.  Biol.  and  Med.,  xm,  No.  2. 

NUSSBAUM,  M.    1905.    Innere  secretion  und  nerveneinfluss.    Ergeb.  Anat.  u.  Entw.,  Bd.  xv. 

SMITH,  G.     1911.     Studies  in  the  experimental  analysis  of  sex.     Quart.  Jour.  Micr.  Sci.,  LVII. 

STEINACH,  E.  1912.  Willkiirliche  Umwandlung  von  Saugetier-Mannchen  in  Tiere  mit 
ausgepragt  weiblichen  Geschlechtscharacteren  und  weiblicher  Psyche.  Arch,  f .  d. 
ges.  Physiol.  CXLIV. 

WALLACE,  A.  R.     1889.    Darwinism. 


GOODALE 


PLATE   I 


NORMAL  ROUEN  DRAKE. 


OODALE 


PLATE  II 


A.  M.  GRAVES  Pi  NX. 


NORMAL  ROUEN  DUCK. 


GOODALE 


PLATE  II 


A.  M.  GRAVER  P'NX. 


AN  OVAKIOTOMIZED  DUCK,  No.  169,  TYPE  I. 


GOODALE 


PLATE   I 


K.    MORITA   PlNX. 


AN  OVABIOTOMIZED  DUCK,  No.  24,  TYPE  II, 


GOODALE 


PLATE 


f> 


THE  EFFECT  OF  OVARIOTOMY  ON  PARTLY-DEVELOPED  FEATHERS. 


3OODALE 


PLATE  vn 


A.  Head  of  capon,  showing  infantile  comb  and  wattles. 

B.  Shanks  of  White  Leghorn  hen  described  on  page  43,  showing  long  spurs. 

C.  Reproductive  system  of  No.  1196;  rb.  right  body  with  duct,    rd,   leading  therefrom; 

Ib,  left  body  and  duct,  Id;  o,  oviduct  (not  clearly  shown  in  the  photograph);  int, 
intestine. 

D.  Two  young  ducks  (No.  169  front  and  No.  171  rear),  showing   condition  soon   after 

castration. 

E.  Wing  of  capon  showing  the  hypertrophied  primary  coverts. 

F.  Partially  ovariotomized  female,  showing  a   few   male   feathers  among  the  female 

feathers.     The  male  feathers  visible  in  the  illustration   are   the   hackle  feathers 
and  the  black  feathers  in  the  wing. 


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